title: Structural aspects and chaperone activity of human HspB3: role of the "C-terminal extension".
abstract: HspB3, an as yet uncharacterized sHsp, is present in muscle, brain, heart, and in fetal tissues. A point mutation correlates with the development of axonal motor neuropathy. We purified recombinant human HspB3. Circular dichroism studies indicate that it exhibits β-sheet structure. Gel filtration and sedimentation velocity experiments show that HspB3 exhibits polydisperse populations with predominantly trimeric species. HspB3 exhibits molecular chaperone-like activity in preventing the heat-induced aggregation of alcohol dehydrogenase (ADH). It exhibits moderate chaperone-like activity towards heat-induced aggregation of citrate synthase. However, it does not prevent the DTT-induced aggregation of insulin, indicating that it exhibits target protein-dependent molecular chaperone-like activity. Unlike other sHsps, it has a very short C-terminal extension. Fusion of the C-terminal extension of αB-crystallin results in altered tertiary and quaternary structure, and increase in polydispersity of the chimeric protein, HspB3αB-CT. The chimeric protein shows comparable chaperone-like activity towards heat-induced aggregation of ADH and citrate synthase. However, it shows enhanced activity towards DTT-induced aggregation of insulin. Our study, for the first time, provides the structural and chaperone functional characterization of HspB3 and also sheds light on the role of the C-terminal extension of sHsps.
authors.affiliation: Centre for Cellular and Molecular Biology, Council for Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad 500 007, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Asthana
authors.forename: Bakthisaran
authors.initials: B
authors.lastname: Raman
authors.forename: Tangirala
authors.initials: T
authors.lastname: Ramakrishna
authors.forename: Ch Mohan
authors.initials: ChM
authors.lastname: Rao
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry; D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D002942:Circular Dichroism; D002950:Citrate (si)-Synthase / Q000737:chemistry; D003634:DDT / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007328:Insulin / Q000737:chemistry; D018832:Molecular Chaperones / Q000737:chemistry*; D008969:Molecular Sequence Data; D025941:Protein Interaction Mapping; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics; D013329:Structure-Activity Relationship; D038203:alpha-Crystallin B Chain / Q000737:chemistry
chemical_list: C116424:HSPB3 protein, human; D006360:Heat-Shock Proteins; D007328:Insulin; D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; D038203:alpha-Crystallin B Chain; D003634:DDT; D000426:Alcohol Dehydrogenase; D002950:Citrate (si)-Synthase