2inq
From Proteopedia
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Neutron Crystal Structure of Escherichia coli Dihydrofolate Reductase Bound to the Anti-cancer drug, Methotrexate
Overview
Hydrogen atoms play a central role in many biochemical processes yet are, difficult to visualize by x-ray crystallography. Spallation neutron, sources provide a new arena for protein crystallography with TOF, measurements enhancing data collection efficiency and allowing hydrogen, atoms to be located in smaller crystals of larger biological, macromolecules. Here we report a 2.2-A resolution neutron structure of, Escherichia coli dihydrofolate reductase (DHFR) in complex with, methotrexate (MTX). Neutron data were collected on a 0.3-mm(3), D(2)O-soaked crystal at the Los Alamos Neutron Scattering Center. This, study provides an example of using spallation neutrons to study protein, dynamics, to identify protonation states directly from nuclear density, maps, and to analyze solvent structure. Our structure reveals that the, occluded loop conformation [monomer (mon.) A] of the DHFR.MTX complex, undergoes greater H/D exchange compared with the closed-loop conformer, (mon. B), partly because the Met-20 and beta(F-G) loops readily exchange, in mon. A. The eight-stranded beta sheet of both DHFR molecules resists, H/D exchange more than the helices and loops. However, the C-terminal, strand, betaH, in mon. A is almost fully exchanged. Several D(2)Os form, hydrogen bonds with exchanged amides. At the active site, the N1 atom of, MTX is protonated and thus charged when bound to DHFR. Several D(2)Os are, observed at hydrophobic surfaces, including two pockets near the, MTX-binding site. A previously unidentified D(2)O hydrogen bonds with the, catalytic D27 in mon. B, stabilizing its negative charge.
About this Structure
2INQ is a Single protein structure of sequence from Escherichia coli with MT1 as ligand. Active as Dihydrofolate reductase, with EC number 1.5.1.3 Full crystallographic information is available from OCA.
Reference
Neutron diffraction studies of Escherichia coli dihydrofolate reductase complexed with methotrexate., Bennett B, Langan P, Coates L, Mustyakimov M, Schoenborn B, Howell EE, Dealwis C, Proc Natl Acad Sci U S A. 2006 Dec 5;103(49):18493-8. Epub 2006 Nov 27. PMID:17130456
Page seeded by OCA on Wed Nov 21 12:23:10 2007
