introduction to protein structure q: whats that? a: something, you get noble prize for... john...
Post on 19-Dec-2015
220 views
TRANSCRIPT
![Page 1: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/1.jpg)
Introduction to Protein Structure
Q:
Whats that?
A:
Something, you get Noble prize for...
John Kendrew & Max Perutz 1962
Structures of myoglobin & hemoglobin
![Page 2: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/2.jpg)
Subjects, covered in this lecture
• Amino acids and their properties
• Peptide geometry
• Secondary structure
• Motifs
• Domains
• Quaternary structure
![Page 3: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/3.jpg)
Why bother about protein structure?
• Gives you an visual image of how proteins look like.
• Study of protein structures allows to gain an insight into how protein really accomplish their function.
• Nobel prizes...
![Page 4: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/4.jpg)
Amino Acids• 20 different ones, sharing a common backbone but varying side chain.
• Classed according to their chemical properties• L-form
![Page 5: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/5.jpg)
nonpolar amino acids
-R group consists of carbon chains
leucine and isoleucine
are structural isomers
![Page 6: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/6.jpg)
nonpolar amino acids
- R group consists of carbon chains
Phenylalanine and tryptophan
have aromatic rings which are flat due to the double
bond networkTryptophan is often
classified as being polar because of the NH group. In
practice, however it has more of hydrophobic
properties
Methionine has a sulphur atom in its
sidechainsulphur has the same
valence as oxygen
Proline has its R group bound to the amino
nitrogen to form a ring network
![Page 7: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/7.jpg)
polar amino acids
- R group consists of carbon, oxygen and nitrogen atoms together they make the sidechain more hydrophilic
Asn and gln have an amide functional
group
Ser and thr are a mix of carbon chains and hydroxyl
functional groups (-OH). Cysteine has a thiol group (-
SH) which is otherwise structurally similar to serinebut not chemically similar
![Page 8: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/8.jpg)
charged amino acids
- R group has a charge at physiological pH (7.4). pK of the charged groups vary
carboxylgroup
carboxylgroup
aminogroup
guanidiniogroup
imidazolegroup, sometimes
chargedMost often classified as a polar amino acid
![Page 9: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/9.jpg)
Cysteine and disulphides
• The almost exclusively only way to covalently link two non-sequential residues is by forming a disulphide bridge
• Formation of disulphide requires an oxidative environment, threfore disulphides are very rare in intracellular proteins but
quite abundant in secretory proteins
![Page 10: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/10.jpg)
Peptide units
• A peptide is a set of covalently bonded amino acids.
• The covalent bond is usually referred as peptide bond
![Page 11: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/11.jpg)
Biochemist’s peptide unit –from N to C – all main chain atoms within the unit lie in the same residue
Structural biologist’s peptide unit – from C to next C - all main chain atoms within the unit lie in a plane
![Page 12: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/12.jpg)
– Angles phi () N-C– Angle psi () C-CO
– Angle omega () C-N
![Page 13: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/13.jpg)
The angle, cis- and trans- peptides• Because of the partly double nature of peptide bond, is
always close to 180o for trans- peptides or 0o for cis- peptides (±30o in exterme cases)
• Cis- peptides are energetically extremely unfavourable (~1000 fold) because of steric clashes between the neighbouring C atoms
![Page 14: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/14.jpg)
• The only exception is peptide bond before proline, where cis- peptide is just 4 times less favourable than trans- peptide, because there are some steric clashes in both cis- and trans- forms
• Proline cis-trans isomerization is an important factor in protein folding, which is why there are special enzymes – prolylpeptydyl isomerases to catalyze the transition from one form to another
![Page 15: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/15.jpg)
• According to statistics, 0.03% of non-proline peptides and 5.2% of X-Pro peptides are in cis- conformation, resulting in a total of 0.3 % cis-peptides
• In most cases cis- peptides, especially non-proline, occur for a good reason, for example to maintain some particular conformation in the active site of enzyme
![Page 16: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/16.jpg)
Main chain conformations (I)
• Only certain combinations of and are allowed, due to steric clashes of backbone atoms and C atom. Plot of these combinations yields the Ramachandran plot.
• All amino acids clusters in specific regions (called allowed regions) except Gly (explains why Glycine is an important amino acid).
![Page 17: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/17.jpg)
![Page 18: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/18.jpg)
• In good quality structures only about 2% of amino acid residues are found in the disallowed regions of Ramachandran plot
• Of course, residues with disallowed conformations often have some important function in proteins
![Page 19: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/19.jpg)
Side chain conformations
• Side chains can have in principle different conformations (rotation of C-C...)
• The observed conformations in protein structures are the ones which are more energetically favourable (rotamers).
![Page 20: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/20.jpg)
Name three amino acids which are very different from others!
Proline • No free amino group• Very rigid• Introduces breaks in helices and strandsGlycine• Lacks a side chain• Can be found anywhere in Ramachandran plot• In proteins often found in flexible regions with unusual
backbone conformationsCysteine• Disulphides
![Page 21: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/21.jpg)
Primary, secondary, tertiary and quaternary structures
![Page 22: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/22.jpg)
The hydrophobic core• The hydrophobic sidechains of protein has a tendency to
cluster together in order to avoid unfavourable contacts with polar water molecules
• As a result, in general, hydrophobic sidechains are located in the interior of protein, forming the hydrophobic core
• Polar and charged amino acids usually are located on the surface of the protein
• Polar and charged residues also can make hydrophobic contacts with their aliphatic carbon atoms
• Polar and charged residues are seldom completely buried within the core and even when they are, the polar groups are almost invariably involved in hydrogen bond formation
![Page 23: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/23.jpg)
The reasons of secondary structure formation
• Since sidechains of hydrophobic residues are located in the hydrophobic core, the mainchain atoms of the same residues in most cases are also within the hydrophobic core
• Since the presence of polar groups in hydrophobic environment is very unfavourable, the main chain N- and O- atoms have to be neutralised by formation of hydrogen bonds
• The two most efficient ways of hydrogen bond formation is to build an alpha helix or a beta sheet
![Page 24: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/24.jpg)
The alpha helix
• 3.6 residues per turn
• the hydrogen bonds are made between residues n and n+4
![Page 25: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/25.jpg)
![Page 26: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/26.jpg)
Variants of alpha helix
• In regular helix, residue n makes a H-bond with residue n+4
• In 310 helix, residue n makes a H-bond with residue n+3. There are 3 residues per turn, connected by 10 atoms, hence the name 310
• In helix, residue n makes a H-bond with residue n+5
• In helix there is a hole left in the middle of helix and in 310 helix the main chain atoms are packed very tightly. None of above is energetically favourable
• 310 and especially helices occur rarely and usually only at the ends of regular helix or as a separate single-turn helix
![Page 27: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/27.jpg)
Handedness of alpha helix
• The helices as well as 310 and helices ale almost exclusively right-handed
• In very rare occasions, left handed and 310 helixes can occur. They are always very short (4- 6 residues) and normally involved in some important function of protein like in active site or ligand binding
• There are about 30 reported cases of left-handed helices. In contrast, the number of known right handed helices is of order of hundreds of thousands
![Page 28: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/28.jpg)
The dipole moment of helix
![Page 29: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/29.jpg)
Good and bad helix formers
• Different side chains have been found to have weak but definite preferences for helix forming ability
• Ala, Glu, Leu and Met are good helix formers• Pro, Gly, Tyr and Ser are very poor helix formers• The above preferences are not strong enough to be
used in accurate secondary structure predictions
![Page 30: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/30.jpg)
Periodic patterns in helices
• The most common location of an a helice is along the outside of protein, with one side of the helix facing the hydrophobic core and other side facing the solvent
• Such a location results in a periodic pattern of alterating hydrophobic and polar residues
• On itself, however, the pattern is not reliable enough for structure prediction, since small hydrophobic residues can face the solvent and some helices are completely buried or completely exposed
![Page 31: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/31.jpg)
Beta sheetsAntiparallel Parallel
![Page 32: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/32.jpg)
A mixed sheet
A mixed sheet is far less common than antiparallel or parallel
![Page 33: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/33.jpg)
Twist in sheets
• Almost all sheets in the known protein structures are twisted
• The twist is always right-handed
![Page 34: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/34.jpg)
Loops• Loops connect secondary structure elements• Loops are located on the surface of protein • In general, main chain nitrogen and carbonyl oxygen atoms do not
make H-bonds each to other in loops• Loops are rich in polar and charged residues• The lenght of loops can vary from 2 to more than 20 residues• Loops are very flexible, which makes them difficult to see in either x-
ray or NMR studies of proteins• Loops frequently participate in forming of ligand binding sites and
enzyme active sites• In homologous protein families loop regions are far less conserved
than secondary stucture elements• Insertions and deletions in homologous protein families occur almost
exclusively in loop regions
![Page 35: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/35.jpg)
Hairpin loops and reverse turns
• Loops, which connect two adjacent antiparallel beta strands are called hairpin loops
• 2 residues long hairpin loops are often called reverse turns, beta turns or simply turns
Type I turn Type II turn
Strand1 Strand2
Hairpin loop
![Page 36: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/36.jpg)
Motifs
• Simple combinations of a few secondary structure elements occur frequently in protein structures
• These units are called supersecondary structure or motifs
• Some motifs can be associated with a specific biological function (e.g. DNA binding)
• Other motifs have no specific biological function alone, but are part of larger structural and functional assemblies
![Page 37: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/37.jpg)
Helix-loop-helix motifs
Calcium binding motifDNA binding motif
![Page 38: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/38.jpg)
The hairpin motif
• Two adjacent anti-parallel strands, joined by a loop
• The hairpin motif can occur both as an isolated unit or as a part of bigger sheet
Bovine trypsin inhibitorSnake venom- erabutoxin
![Page 39: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/39.jpg)
24 different ways to connect two hairpins
• Only the first 8 arrangements exist in known proteins
![Page 40: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/40.jpg)
The Greek key motif
• The most common way to connect 4 adjacent antiparallel strands
The Greek key motif in Staphilococcus nuclease
![Page 41: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/41.jpg)
The motif
• A convinient way to connect two paralel beta strands
• motif is a part of almost all proteins, containing a paralel beta sheet
![Page 42: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/42.jpg)
The handedness of motif
• Theoretically, two distinct “hands” can exist in motif, with a helice above or below the plane of beta sheet
• In almost all cases the right handed motif exists
R L
![Page 43: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/43.jpg)
Domains
• Domain ia a polypeptide chain or a part of a polypeptide chain that can fold indepedently in a stable tertiary structure with its own hydrophobic core
• Domains can be formed from several simple motifs and additional secondary structure elements
• Proteins can have anything from one to several tens of domains
• In proteins with sevaral domains, most often each domain is associated with a distinct biological function
![Page 44: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/44.jpg)
2x hairpin + strand
16x
2x Greek key
![Page 45: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/45.jpg)
• Domains are most often, but not always continuous pieces of primary structure
N C
N C
N C
![Page 46: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/46.jpg)
Example of proteins with several domains - lac repressor
C-terminal helix (tetramerization)
Helix-turn-helix domain (binds to DNA)hinge helix
Core domain, containing two subdomains, which in turn contain several motifs (binds ligand)
![Page 47: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/47.jpg)
Intact IgG contains 12 immunoglobulin-like domains
Each domain is made of two beta sheets with a topology similar to two Greek key motifs
![Page 48: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/48.jpg)
The quaternary structure
• Some proteins are biologically active as monomers. For those proteins quaternary structure does not exist
• Other proteins, however, are active as homo- or hetero- polymers
• The simplest case and by far the most common form of quaternary structure is a homodimer
• The monomers in homopolymers are often arranged in a symmetric fashion with one or several symmetry axes going through the molecule or some sort of helical arrangement
• Some biologically active units have a very complicated quaternary structure –like ribosomes or viral capsids
![Page 49: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/49.jpg)
2-fold symmetry in Glutahione-S-transferase
![Page 50: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/50.jpg)
9-fold symmetry in light-harvesting complex II
from Rhodopseudomonas acidophila.
![Page 51: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/51.jpg)
222 symmetry in prealbumin
![Page 52: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/52.jpg)
A simple icosahedral virus – 180 chemically identical subunits
![Page 53: Introduction to Protein Structure Q: Whats that? A: Something, you get Noble prize for... John Kendrew & Max Perutz 1962 Structures of myoglobin & hemoglobin](https://reader036.vdocuments.net/reader036/viewer/2022062320/56649d375503460f94a10157/html5/thumbnails/53.jpg)
Small subunit of ribosome: a lot of different proteins, no symmetry