L. O. Ford, L. Johnson, P. Machin
Sep 15, 1974
Citations
2
Influential Citations
138
Citations
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Journal
Journal of molecular biology
Abstract
Abstract The binding of a proposed transition-state analogue, the δ-lactone derived from tetra- N -acetylchitotetraose, to lysozyme in the crystal at pH 2.6 has been studied by X-ray diffraction techniques to a resolution of 2.5 A. The tetrasaccharide lactone is bound in sites A, B, C, D with sugar residues located in sites A, B and C in similar positions to those observed previously in the complex with tri- N -acetylchitotriose. Analysis of the electron density map for site D, by direct model-building and with a computer model-building programme, indicates that the δ-lactone ring is in a conformation close to a sofa or a boat which brings the hydroxymethyl group C (6) O (6) axial. These studies provide support for the role of strain in the proposed mechanism of lysozyme catalysis. The orientation of the lactone group in site D is slightly different from that originally derived by hypothetical model-building.