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Spontaneous asparaginyl deamidation of canine milk lysozyme under mild conditions
Author(s) -
aka Yasuhiro,
Aizawa Tomoyasu,
Akieda Daisuke,
Yasui Masanori,
Watanabe Masahiro,
Watanabe Nobuhisa,
Tanaka Isao,
Kamiya Masakatsu,
Mizuguchi Mineyuki,
Demura Makoto,
Kawano Keiichi
Publication year - 2008
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.21927
Subject(s) - deamidation , lysozyme , chemistry , residue (chemistry) , molten globule , biochemistry , protein structure , biophysics , enzyme , biology
Asparaginyl deamidation is a common form of nonenzymatic degradation of proteins and peptides. As it introduces a negative charge spontaneously and irreversibly, charge heterogeneity can be accumulated in protein solution during purification, preservation, and experiments. In this study, canine milk lysozyme (CML), a useful model for the study of the molten globule state, exhibited charge heterogeneity after sample purification. Four Asn residues in CML deamidated rapidly under mild conditions: pH 8.0 and 30°C. Other than these residues, one Asn residue, which was stable in the native state, was labile to deamidation in the unfolded state. This suggests that the structural formation around Asn can suppress deamidation. Substitutions of these labile Asn residues to Gln residues prevented deamidation effectively. Because the substitutions did not disrupt the structural formation of the native and molten globule states, they will enable more precise analyses for physical and structural studies. Proteins 2008. © 2008 Wiley‐Liss, Inc.