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Publication Abstract from PubMed

Cold shock proteins (Csp) constitute a family of ubiquitous small proteins that act as RNA-chaperones to avoid cold-induced termination of translation. All members contain two subdomains composed of 2 and 3 beta-strands respectively, which are connected by a hinge loop and fold into a beta-barrel. Bacillus caldolyticus Csp (BcCsp) is one of the most studied members of the family in terms of its folding, function and structure. This protein has been described as a monomer in solution, although a recent crystal structure showed dimerization via domain swapping (DS). In contrast, other cold shock proteins of the same fold are known to dimerize in a non-swapped arrangement. Hypothesizing that reducing the size of the hinge loop may promote swapping as in several other DS proteins with different folds we deleted two residues from these region (BcCsp36-37), leading to a protein in monomer-dimer equilibrium with similar folding stability to that of the wild-type. Strikingly, the crystal structure of BcCsp36-37 revealed a non-swapped dimer with its interface located at the nucleic acid-binding surface, showing that the deletion led to structural consequences far from the perturbation site. Concomitantly, circular dichroism experiments on BcCsp36-37 demonstrated that binding of the oligonucleotide hexathymidine disrupts the dimer. Additionally, HDXMS shows a protective effect on the protein structure upon dimerization, where the resulting interactions between ligand-binding surfaces in the dimer reduced the extent of exchange throughout the whole protein. Our work provides evidence of the complex interplay between conformational dynamics, deletions and oligomerization within the Csp protein family. This article is protected by copyright. All rights reserved.

Unusual dimerization of a BcCsp mutant leads to reduced conformational dynamics.,Carvajal AI, Vallejos G, Komives EA, Castro-Fernandez V, Leonardo DA, Garratt RC, Ramirez-Sarmiento CA, Babul J FEBS J. 2017 Apr 29. doi: 10.1111/febs.14093. PMID:28457014^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.