1MEN

complex structure of human GAR Tfase and substrate beta-GAR

Summary for 1MEN

• Entry DOI: 10.2210/pdb1men/pdb
• Related: 1MEJ 1MEO
• Descriptor: Phosphoribosylglycinamide formyltransferase, GLYCINAMIDE RIBONUCLEOTIDE (3 entities in total)
• Functional Keywords: purine biosynthesis, substrate-enzyme complex, transferase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 3
• Total formula weight: 73220.38

Authors

Zhang, Y.,Desharnais, J.,Greasley, S.E.,Beardsley, G.P.,Boger, D.L.,Wilson, I.A. (deposition date: 2002-08-08, release date: 2002-12-18, Last modification date: 2023-09-20)

Primary citation

Zhang, Y.,Desharnais, J.,Greasley, S.E.,Beardsley, G.P.,Boger, D.L.,Wilson, I.A.
Crystal structures of human GAR Tfase of low and high pH and with substrate beta-GAR
Biochemistry, 41:14206-14215, 2002

PubMed Abstract: Glycinamide ribonucleotide transformylase (GAR Tfase) is a key folate-dependent enzyme in the de novo purine biosynthesis pathway and, as such, has been the target for antitumor drug design. Here, we describe the crystal structures of the human GAR Tfase (purN) component of the human trifunctional protein (purD-purM-purN) at various pH values and in complex with its substrate. Human GAR Tfase exhibits pH-dependent enzyme activity with its maximum around pH 7.5-8. Comparison of unliganded human GAR Tfase structures at pH 4.2 and pH 8.5 reveals conformational differences in the substrate binding loop, which at pH 4.2 occupies the binding cleft and prohibits substrate binding, while at pH 8.5 is permissive for substrate binding. The crystal structure of GAR Tfase with its natural substrate, beta-glycinamide ribonucleotide (beta-GAR), at pH 8.5 confirms this conformational isomerism. Surprisingly, several important structural differences are found between human GAR Tfase and previously reported E. coli GAR Tfase structures, which have been used as the primary template for drug design studies. While the E. coli structure gave valuable insights into the active site and formyl transfer mechanism, differences in structure and inhibition between the bacterial and mammalian enzymes suggest that the human GAR Tfase structure is now the appropriate template for the design of anti-cancer agents.

PubMed: 12450384
DOI: 10.1021/bi020522m

Experimental method

X-RAY DIFFRACTION (2.23 Å)