Download MendeleyN-terminal domain of {alpha}B-crystallin provides a conformational switch for multimerization and structural heterogeneity.
Jehle, S., Vollmar, B.S., Bardiaux, B., Dove, K.K., Rajagopal, P., Gonen, T., Oschkinat, H., Klevit, R.E.(2011) Proc Natl Acad Sci U S A 108: 6409-6414
- PubMed: 21464278
- DOI: https://doi.org/10.1073/pnas.1014656108
- Primary Citation of Related Structures:
3J07 - PubMed Abstract:
The small heat shock protein (sHSP) αB-crystallin (αB) plays a key role in the cellular protection system against stress. For decades, high-resolution structural studies on heterogeneous sHSPs have been confounded by the polydisperse nature of αB oligomers. We present an atomic-level model of full-length αB as a symmetric 24-subunit multimer based on solid-state NMR, small-angle X-ray scattering (SAXS), and EM data. The model builds on our recently reported structure of the homodimeric α-crystallin domain (ACD) and C-terminal IXI motif in the context of the multimer. A hierarchy of interactions contributes to build multimers of varying sizes: Interactions between two ACDs define a dimer, three dimers connected by their C-terminal regions define a hexameric unit, and variable interactions involving the N-terminal region define higher-order multimers. Within a multimer, N-terminal regions exist in multiple environments, contributing to the heterogeneity observed by NMR. Analysis of SAXS data allows determination of a heterogeneity parameter for this type of system. A mechanism of multimerization into higher-order asymmetric oligomers via the addition of up to six dimeric units to a 24-mer is proposed. The proposed asymmetric multimers explain the homogeneous appearance of αB in negative-stain EM images and the known dynamic exchange of αB subunits. The model of αB provides a structural basis for understanding known disease-associated missense mutations and makes predictions concerning substrate binding and the reported fibrilogenesis of αB.
Organizational Affiliation:
Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
