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Crystal structure of a mutant human lysozyme with a substituted disulfide bond
Author(s) -
Inaka Koji,
Kanaya Eiko,
Kikuchi Masakazu,
Miki Kunio
Publication year - 2001
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.1054
Subject(s) - crystallography , lysozyme , chemistry , folding (dsp implementation) , molecule , mutant , protein structure , protein folding , crystal structure , disulfide bond , stereochemistry , biochemistry , organic chemistry , electrical engineering , gene , engineering
Abstract The three‐dimensional structure of a mutant human lysozyme, W64CC65A, in which a non‐native disulfide bond Cys64Cys81 is substituted for the Cys65Cys81 of the wild type protein by replacing Trp64 and Cys65 with Cys and Ala, respectively, was determined by X‐ray crystallography and refined to an R ‐value of 0.181, using 33,187 reflections at 1.87‐Å resolution. The refined model of the W64CC65A protein consisted of four molecules, which were related by two noncrystallographic twofold axes and a translation vector. Although no specific structural differences could be observed among these four molecules, the overall B‐factors of each molecule were quite different. The overall structure of W64CC65A, especially in the α‐helical domain, was found to be quite similar to that of the wild type protein. Moreover, the side‐chain conformation of the newly formed Cys64Cys81 bond was quite similar to that of the Cys65Cys81 bond of the wild‐type protein. However, in the β‐sheet domain, the main‐chain atoms of the loop region from positions 66–75 could not be determined, and significant structural changes due to the formation of the non‐native disulfide bond could be observed. From these results, it is clear that the loop region of the mutant protein does not fold with the specific folding as observed in the wild‐type protein. Proteins 2001;43:413–419. © 2001 Wiley‐Liss, Inc.