2h5c

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spinqualitylabelsall models 2h5c, resolution 0.82Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

0.82A resolution crystal structure of alpha-lytic protease at pH 5

Overview

To address questions regarding the mechanism of serine protease catalysis, we have solved two X-ray crystal structures of alpha-lytic protease, (alphaLP) that mimic aspects of the transition states: alphaLP at pH 5, (0.82 A resolution) and alphaLP bound to the peptidyl boronic acid, inhibitor, MeOSuc-Ala-Ala-Pro-boroVal (0.90 A resolution). Based on these, structures, there is no evidence of, or requirement for, histidine-flipping during the acylation step of the reaction. Rather, our, data suggests that upon protonation of His57, Ser195 undergoes a, conformational change that destabilizes the His57-Ser195 hydrogen bond, preventing the back-reaction. In both structures the His57-Asp102 hydrogen, bond in the catalytic triad is a normal ionic hydrogen bond, and not a, low-barrier hydrogen bond (LBHB) as previously hypothesized. We propose, that the enzyme has evolved a network of relatively short hydrogen bonds, that collectively stabilize the transition states. In particular, a short, ionic hydrogen bond (SIHB) between His57 Nepsilon2 and the substrate's, leaving group may promote forward progression of the TI1-to-acylenzyme, reaction. We provide experimental evidence that refutes use of either a, short donor-acceptor distance or a downfield 1H chemical shift as sole, indicators of a LBHB.

About this Structure

2H5C is a Single protein structure of sequence from Lysobacter enzymogenes with SO4 and GOL as ligands. Active as Alpha-lytic endopeptidase, with EC number 3.4.21.12 Full crystallographic information is available from OCA.

Reference

Subangstrom crystallography reveals that short ionic hydrogen bonds, and not a His-Asp low-barrier hydrogen bond, stabilize the transition state in serine protease catalysis., Fuhrmann CN, Daugherty MD, Agard DA, J Am Chem Soc. 2006 Jul 19;128(28):9086-102. PMID:16834383

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