期刊
ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY
卷 74, 期 -, 页码 264-278出版社
INT UNION CRYSTALLOGRAPHY
DOI: 10.1107/S2059798318000207
关键词
protein crystallography; protein structure; crystal dehydration; conformational heterogeneity; lysozyme; variable-temperature crystallography; protein-solvent interactions
资金
- NSF [MCB-1330685]
- Cornell University's Molecular Biophysics Training Grant [NIH T32GM0082567]
- National Science Foundation
- National Institutes of Health/National Institute of General Medical Sciences under NSF [DMR-0936384]
- National Institutes of Health through its National Institute of General Medical Sciences [GM-103485]
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [P41GM103485] Funding Source: NIH RePORTER
- Direct For Biological Sciences [1330685] Funding Source: National Science Foundation
The modulation of main-chain and side-chain conformational heterogeneity and solvent structure in monoclinic lysozyme crystals by dehydration (related to water activity) and temperature is examined. Decreasing the relative humidity (from 99 to 11%) and decreasing the temperature both lead to contraction of the unit cell, to an increased area of crystal contacts and to remodeling of primarily contact and solvent-exposed residues. Both lead to the depopulation of some minor side-chain conformers and to the generation of new conformations. Side-chain modifications and main-chain r.m.s.d.s associated with cooling from 298 to 100 K depend on relative humidity and are minimized at 85% relative humidity (r.h.). Dehydration from 99 to 93% r.h. and cooling from 298 to 100 K result in a comparable number of remodeled residues, with dehydration-induced remodeling somewhat more likely to arise from contact interactions. When scaled to equivalent temperatures based on unit-cell contraction, the evolution of side-chain order parameters with dehydration shows generally similar features to those observed on cooling to T = 100 K. These results illuminate the qualitative and quantitative similarities between structural perturbations induced by modest dehydration, which routinely occurs in samples prepared for 298 and 100 K data collection, and cryocooling. Differences between these perturbations in terms of energy landscapes and occupancies, and implications for variable-temperature crystallography between 180 and 298 K, are discussed. It is also noted that remodeling of a key lysozyme active-site residue by dehydration, which is associated with a radical decrease in the enzymatic activity of lysozyme powder, arises due to a steric clash with the residue of a symmetry mate.
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