dihydrofolate reductase (dhfr)
DESCRIPTION
DHFR is a key enzyme in folate metabolism DHFR is a key enzyme in folate metabolism. It contributes to the de novo mitochondrial thymidylate biosynthesis pathway. Catalyzes an essential reaction for de novo glycine and purine synthesis, and for DNA precursor synthesis. Binds its own mRNA and that of DHFRL1. The DHFR gene is located on long (q) arm of chromosome 5 between positions 11.2 and 13.2. More precisely, the DHFR gene is located from base pair 80,626,225 to base 80,654,980 on chromosome 5 . DHFR catalyzes the transfer of a hydride from NADPH to dihydrofolate with an accompanying protonation to produce tetrahydrofolate. In the end, dihydrofolate is reduced to tetrahydrofolate and NADPH is oxidized to NAPD+. Background Found in all organisms: Bacteria Human Virus Encoded by DHFR gene that exists in chromosome 5 Homo Dimer Bind substrates Catalyze enzyme DNA precursor synthesis De novo mitochondrial thymidylate biosynthesis pathwayTRANSCRIPT
Dihydrofolate Reductase (DHFR)
Ruixiao Ray Gao Department of chemistry Illinois state university
10/30/2014 DHFR is a key enzyme in folate metabolism
DHFR is a key enzyme in folate metabolism. It contributes to the de
novo mitochondrial thymidylate biosynthesis pathway. Catalyzes an
essential reaction for de novo glycine and purine synthesis, and
for DNA precursor synthesis. Binds its own mRNA and that of DHFRL1.
The DHFR gene is located on long (q) arm of chromosome 5 between
positions 11.2 and More precisely, the DHFR gene is located from
base pair 80,626,225 to base 80,654,980 on chromosome 5 . DHFR
catalyzes the transfer of a hydride from NADPHtodihydrofolate with
an accompanying protonation to produce tetrahydrofolate. In the
end, dihydrofolate is reduced to tetrahydrofolate and NADPH is
oxidized to NAPD+. Background Found in all organisms: Bacteria
Human Virus Encoded by DHFR gene that exists in chromosome Homo
Dimer Bind substratesCatalyze enzymeDNA precursor synthesisDe novo
mitochondrial thymidylatebiosynthesis pathway structure This figure
shows the structure of DHFR isoform, staphylococcus aureus, by
using Rasmol through NCBI with PDB ID: 3FRA. Rasmol displayed 3D
saDHFR structure is in cartoon diagram with alpha helices in pink
and beta sheets in yellow. There are three alpha helices positions
in this amino acids sequence shown above, helix 12, helix 11, and
helix 16. This string is defined from residue with 1984 atoms
selected. Each particular helix has couple of interactions in
theory stabilize the alpha helix such as serine 24 bound with
glycine 39, glycine 102 and glutamic acid 112, serine 81 and
glycine 9. However, the helix with side chain interaction may also
destabilize the overall structure, such as helix 8 with arginine 45
and glycine 52. These amino acid side chains cant form either
hydrogen bond, or attract each other, therefore destabilize overall
helix Amino Acid Sequence Alignment
Residues Met20 or loop 1 and, along with other loops, are part of
the major subdomain that surround the active site.The active site
is situated in the N-terminal half of the sequence, which includes
a conserved Pro-Trp PW) dipeptide; the tryptophan has been shown to
be involved in the binding of substrate by the enzyme. Met20 Green:
Major AA to bind substrates in active site Red: Residue Met20/Loop
1 as one of major subdomains Light Grey: Beta Sheets Stick on Loop:
Met20 Blue: Ser24 & Gly39
Pink:alpha helice Light Grey: Beta Sheets Stick on Loop:Met20
Blue:Ser24 & Gly39 Sticks: Gly102 & Glu112 Ser81 & Gly9
Blue & sticks on helices are used to stablize alpha helices
through hydrogen bonding Anticancer Properties
Antimalarial drugs for their anticancer potential: DHFR inhibitors
resist the growth of several human cancer lines Bind with
pyrimethamine and P218 Cluster analysis clustered tighly the
synthetic peroxides and DHFR inhibitors. Artemisinins &
paclitaxel with DHFR inhibitors kill cancer cells by inducing
apoptosis DHFR Mutants (A) Dimer structure of TS-DHFR. TS and DHFR
domains are labeled. Crossover helix and Helix B are also labeled
in the DHFR domains. The DHFR ligands, NADP+ and H2F are shown in
sticks. (B) Close-up of the crossover helix region. Residues on the
crossover helix (light grey) are displayed as well as residues on
the active site helix (dark grey). (C) Space filling representation
highlighting the close interactions of the crossover helix (light
grey) and helix B (dark grey) residues. DHFR active site ligands
are shown in sticks.Plots show the rate constant of single DHFR
turnover reactions, results indicate that binding with mutated DHFR
proteins will significantly decrease the protein catalyst
reactivity because the amino acid side chains will become nonpolar
with no charge which cant form either hydrogen bond, or attract any
other substrates/enzymes. Thank you