A critical motif for oligomerization and chaperone activity of bacterial α-heat shock proteins

被引:79
作者
Studer, S [1 ]
Obrist, M [1 ]
Lentze, N [1 ]
Narberhaus, F [1 ]
机构
[1] Swiss Fed Inst Technol, Inst Microbiol, Zurich, Switzerland
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 2002年 / 269卷 / 14期
关键词
alpha-crystallin; alpha-heat shock protein; small heat shock protein; chaperone; oligomerization;
D O I
10.1046/j.1432-1033.2002.03049.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Oligomerization into multimeric complexes is a prerequisite for the chaperone function of almost all alpha-crystallin type heat shock proteins (alpha-Hsp), but the molecular details of complex assembly are poorly understood. The alpha-Hsp proteins from Bradyrhizobium japonicum are suitable bacterial models for structure-function studies of these ubiquitous stress proteins. They fall into two distinct classes, A and B, display chaperone activity in vitro and form oligomers of approximate to 24 subunits. We constructed 19 derivatives containing truncations or point mutations within the N- and C-terminal regions and analyzed them by gel filtration, citrate synthase assay and coaffinity purification. Truncation of more than the initial few amino acids of the N-terminal region led to the formation of distinct dimeric to octameric structures devoid of chaperone activity. In the C-terminal extension, integrity of an isoleucine-X-isoleucine (I-X-I) motif was imperative for alpha-Hsp functionality. This I-X-I motif is one of the characteristic consensus motifs of the alpha-Hsp family, and here we provide experimental evidence of its structural and functional importance. alpha-Hsp proteins lacking the C-terminal extension were inactive, but still able to form dimers. Here, we demonstrate that the central alpha-crystallin domain alone is not sufficient for dimerization. Additional residues at the end of the N-terminal region were required for the assembly of two subunits.
引用
收藏
页码:3578 / 3586
页数:9
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