The Role of Intrinsically Disordered Regions in the Structure and Functioning of Small Heat Shock Proteins

Author(s): Maria V. Sudnitsyna, Evgeny V. Mymrikov, Alim S. Seit-Nebi, Nikolai B. Gusev.

Journal Name: Current Protein & Peptide Science

Volume 13 , Issue 1 , 2012

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Abstract:

Small heat shock proteins (sHsp) form a large ubiquitous family of proteins expressed in all phyla of living organisms. The members of this family have low molecular masses (13-43 kDa) and contain a conservative α-crystallin domain. This domain (about 90 residues) consists of several β-strands forming two β-sheets packed in immunoglobulinlike manner. The α-crystallin domain plays an important role in formation of stable sHsp dimers, which are the building blocks of the large sHsp oligomers. A large N-terminal domain and a short C-terminal extension flank the α-crystallin domain. Both the N-terminal domain and the C-terminal extension are flexible, susceptible to proteolysis, prone to posttranslational modifications, and are predominantly intrinsically disordered. Differently oriented N-terminal domains interact with each other, with the core α-crystallin domain of the same or neighboring dimers and play important role in formation of large sHsp oligomers. Phosphorylation of certain sites in the N-terminal domain affects the sHsp quaternary structure, the sHsp interaction with target proteins and the sHsp chaperone-like activity. The C-terminal extension often carrying the conservative tripeptide (I/V/L)-X-(I/V/L) is capable of binding to a hydrophobic groove on the surface of the core α-crystallin domain of neighboring dimer, thus affecting the plasticity and the overall structure of sHsp oligomers. The Cterminal extension interacts with target proteins and affects their interaction with the α-crystallin domain increasing solubility of the complexes formed by sHsp and their targets. Thus, disordered N- and C-terminal sequences play important role in the structure, regulation and functioning of sHsp.

Keywords: Intrinsic disorder, protein-protein interaction, phosphorylation, small heat shock proteins, sHsp, DNAJ, axonopodis, Methanococcus jannaschii, Xanthomonas, HspA

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Article Details

VOLUME: 13
ISSUE: 1
Year: 2012
Page: [76 - 85]
Pages: 10
DOI: 10.2174/138920312799277875

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