title: Multilevel structural characteristics for the natural substrate proteins of bacterial small heat shock proteins.
abstract: Small heat shock proteins (sHSPs) are ubiquitous molecular chaperones that prevent the aggregation of various non-native proteins and play crucial roles for protein quality control in cells. It is poorly understood what natural substrate proteins, with respect to structural characteristics, are preferentially bound by sHSPs in cells. Here we compared the structural characteristics for the natural substrate proteins of Escherichia coli IbpB and Deinococcus radiodurans Hsp20.2 with the respective bacterial proteome at multiple levels, mainly by using bioinformatics analysis. Data indicate that both IbpB and Hsp20.2 preferentially bind to substrates of high molecular weight or moderate acidity. Surprisingly, their substrates contain abundant charged residues but not abundant hydrophobic residues, thus strongly indicating that ionic interactions other than hydrophobic interactions also play crucial roles for the substrate recognition and binding of sHSPs. Further, secondary structure prediction analysis indicates that the substrates of low percentage of β-sheets or coils but high percentage of α-helices are un-favored by both IbpB and Hsp20.2. In addition, IbpB preferentially interacts with multi-domain proteins but unfavorably with α + β proteins as revealed by SCOP analysis. Together, our data suggest that bacterial sHSPs, though having broad substrate spectrums, selectively bind to substrates of certain structural features. These structural characteristic elements may substantially participate in the sHSP-substrate interaction and/or increase the aggregation tendency of the substrates, thus making the substrates more preferentially bound by sHSPs.
authors: State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China.
authors: Xinmiao
authors: X
authors: Fu
authors: Zengyi
authors: Z
authors: Chang
authors: Xiaodong
authors: X
authors: Shi
authors: Dongbo
authors: D
authors: Bu
authors: Chao
authors: C
authors: Wang
mesh_terms: D034301:Deinococcus / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry*; D050886:HSP20 Heat-Shock Proteins / Q000737:chemistry*; D006360:Heat-Shock Proteins / Q000737:chemistry*; D050888:Heat-Shock Proteins, Small / Q000737:chemistry*; D018832:Molecular Chaperones / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013379:Substrate Specificity
chemical_list: D029968:Escherichia coli Proteins; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D050888:Heat-Shock Proteins, Small; C097579:IbpB protein, E coli; D018832:Molecular Chaperones
keywords: Hsp20.2; IbpB; molecular chaperone; protein aggregation; small heat shock protein; substrate proteins