The Small Heat-Shock Proteins HSPB2 and HSPB3 Form Well-defined Heterooligomers in a Unique 3 to 1 Subunit Ratio

JOURNAL OF MOLECULAR BIOLOGY

卷:393

Article

den Engelsman, John¹  Boros, Sandor¹  Dankers, Patricia Y. W.¹  Kamps, Bram¹  Egberts, Wilma T. Vree¹  Boede, Csaba S.²  Lane, Laura A.³  Aquilina, J. Andrew⁴  Benesch, Justin L. P.³  Robinson, Carol V.³  de Jong, Wilfried W.¹  Boelens, Wilbert C.¹ 

[1] Radboud Univ Nijmegen, Dept Biomol Chem 271, Nijmegen Ctr Mol Life Sci, Inst Mol & Mat, NL-6500 HB Nijmegen, Netherlands

[2] Semmelweis Univ, Dept Biophys & Radiat Biol, H-1085 Budapest, Hungary

[3] Univ Cambridge, Dept Chem, Cambridge CB2 1EW, England

[4] Univ Wollongong, Sch Biol Sci, Wollongong, NSW, Australia

关键词: molecular chaperones;    crystallin;    small heat-shock protein;    heterooligomers;    MKBP;   

DOI  :  10.1016/j.jmb.2009.08.052

来源: Elsevier

【 摘 要 】

Various mammalian small heat-shock proteins (sHSPs) can interact with one another to form large polydisperse assemblies. In muscle cells, HSPB2/MKBP (myotonic dystrophy protein kinase-binding protein) and HSPB3 have been shown to form an independent complex. To date, the biochemical properties of this complex have not been thoroughly characterized. In this study, we show that recombinant HSPB2 and HSPB3 can be successfully purified from Escherichia coli cells co-expressing both proteins. Nanoelectrospray ionization mass spectrometry and sedimentation velocity analytical ultracentrifugation analysis showed that HSPB2/B3 forms a series of well defined hetero-oligomers, consisting of 4, 8, 12, 16, 20 and 24 subunits, each maintaining a strict 3:1 HSPB2/HSPB3 subunit ratio. These complexes are thermally stable up to 40 degrees C, as determined by far-UV circular dichroism spectroscopy. Surprisingly, HSPB2/B3 exerted a poor chaperone-like and thermoprotective activity, which is likely related to the low surface hydrophobicity, as revealed by its interaction with the hydrophobic probe 1-anilino-8-naphthalenesulfonic acid. Co-immunoprecipitation experiments demonstrated that the HSPB2/B3 oligomer cannot interact with HSP20, HSP27 or alpha B-crystallin, whereas the homomeric form of HSPB2, thus not in complex with HSPB3, could associate efficiently with HSP20. Taken altogether, this study provides evidence that, despite the high level of sequence homology within the sHSP fan-Lily the biochemical properties of the HSPB2/B3 complex are distinctly different from those of other sHSPs, indicating that the HSPB2/B3 assembly is likely to possess cellular functions other than those of its family members. (C) 2009 Elsevier Ltd. All rights reserved.

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