Structural Studies on the Oligomeric Transition of a Small Heat Shock Protein, StHsp14.0

• Published in: Journal of molecular biology 2012-09, Vol.422 (1), p.100-108
• Main Authors: Hanazono, Yuya, Takeda, Kazuki, Yohda, Masafumi, Miki, Kunio
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Archaeal Proteins - chemistry; Archaeal Proteins - metabolism; binding sites; chaperone; Chromatography, Gel; Circular Dichroism; crystal structure; Crystallography, X-Ray; Dimerization; heat shock proteins; Heat-Shock Proteins, Small - chemistry; Heat-Shock Proteins, Small - metabolism; Molecular Sequence Data; multiple weak interaction; oligomeric transition; Protein Denaturation; Protein Folding; self-assembly; size exclusion chromatography; Sulfolobus; Sulfolobus - metabolism
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2012.05.017

The small heat shock proteins (sHsps), which are widely found in all domains of life, bind and stabilize denatured proteins to prevent aggregation. The sHsps exist as large oligomers that are composed of 9–40 subunits and control their chaperone activity by the transition of the oligomeric state. Though the oligomeric transition is important for the biological function of most sHsps, atomic details have not been elucidated. Here, we report crystal structures in both the 24-meric and dimeric states for an sHsp, StHsp14.0 from Sulfolobus tokodaii, in order to reveal changes upon the oligomeric transition. The results indicate that StHsp14.0 forms a spherical 24-mer with a diameter of 115 Å. The diameter is defined by the inter-monomer angle in the dimer. The dimer structure in the dimeric state shows only small differences from that in the 24-meric state. Some significant differences are exclusively observed at the binding site for the C-terminus. Although a dimer has four interactive sites with neighboring dimers, the weakness of the respective interactions is indicated from the size-exclusion chromatography. The small structural changes imply an activation mechanism mediated by multiple weak interactions. [Display omitted] ► Crystal structures in the 24-meric and dimeric states of StHsp14.0 were determined. ► Structural differences are exclusively observed at the binding site for C-terminus. ► The dimer structure is ready for the formation of the 24-mer. ► The respective interactions between the IXI/V motif and the binding site are very weak. ► The small structural changes imply an activation mediated by weak interactions.