2p4s
From Proteopedia
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Structure of Purine Nucleoside Phosphorylase from Anopheles gambiae in complex with DADMe-ImmH
Overview
The purine salvage pathway of Anopheles gambiae, a mosquito that transmits, malaria, has been identified in genome searches on the basis of sequence, homology with characterized enzymes. Purine nucleoside phosphorylase (PNP), is a target for the development of therapeutic agents in humans and purine, auxotrophs, including malarial parasites. The PNP from Anopheles gambiae, (AgPNP) was expressed in Escherichia coli and compared to the PNPs from, Homo sapiens (HsPNP) and Plasmodium falciparum (PfPNP). AgPNP has kcat, values of 54 and 41 s-1 for 2'-deoxyinosine and inosine, its preferred, substrates, and 1.0 s-1 for guanosine. However, the chemical step is fast, for AgPNP at 226 s-1 for guanosine in pre-steady-state studies., 5'-Deaza-1'-aza-2'-deoxy-1'-(9-methylene)-Immucillin-H (DADMe-ImmH) is a, transition-state mimic for a 2'-deoxyinosine ribocation with a fully, dissociated N-ribosidic bond and is a slow-onset, tight-binding inhibitor, with a dissociation constant of 3.5 pM. This is the tightest-binding, inhibitor known for any PNP, with a remarkable Km/Ki* of 5.4 x 10(7), and, is consistent with enzymatic transition state predictions of enhanced, transition-state analogue binding in enzymes with enhanced catalytic, efficiency. Deoxyguanosine is a weaker substrate than deoxyinosine, and, DADMe-Immucillin-G is less tightly bound than DADMe-ImmH, with a, dissociation constant of 23 pM for AgPNP as compared to 7 pM for HsPNP., The crystal structure of AgPNP was determined in complex with DADMe-ImmH, and phosphate to a resolution of 2.2 A to reveal the differences in, substrate and inhibitor specificity. The distance from the N1' cation to, the phosphate O4 anion is shorter in the AgPNP.DADMe-ImmH.PO4 complex than, in HsPNP.DADMe-ImmH.SO4, offering one explanation for the stronger, inhibitory effect of DADMe-ImmH for AgPNP.
About this Structure
2P4S is a Single protein structure of sequence from Anopheles gambiae with and as ligands. Active as Purine-nucleoside phosphorylase, with EC number 2.4.2.1 Full crystallographic information is available from OCA.
Reference
Anopheles gambiae purine nucleoside phosphorylase: catalysis, structure, and inhibition., Taylor EA, Rinaldo-Matthis A, Li L, Ghanem M, Hazleton KZ, Cassera MB, Almo SC, Schramm VL, Biochemistry. 2007 Oct 30;46(43):12405-15. Epub 2007 Oct 6. PMID:17918964
Page seeded by OCA on Wed Jan 23 11:06:51 2008
