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BioMed Research International
Volume 2013 (2013), Article ID 162674, 8 pages
http://dx.doi.org/10.1155/2013/162674
Research Article

Thermal and Chemical Stability of Two Homologous POZ/BTB Domains of KCTD Proteins Characterized by a Different Oligomeric Organization

1Istituto di Cristallografia, CNR, Via G. Amendola 122/O, 70126 Bari, Italy
2DFM Scarl, Via Mezzocannone 16, 80134 Napoli, Italy
3Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, 80134 Napoli, Italy
4Kedrion S.p.A, S. Antimo, 80029 Napoli, Italy
5Dipartimento di Scienze per la Biologia, la Geologia e l’Ambiente, Università del Sannio, Via Port’Arsa 11, 82100 Benevento, Italy

Received 26 June 2013; Revised 11 September 2013; Accepted 18 September 2013

Academic Editor: D. M. Clarke

Copyright © 2013 Luciano Pirone et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

POZ/BTB domains are widespread modules detected in a variety of different biological contexts. Here, we report a biophysical characterization of the POZ/BTB of KCTD6, a protein that is involved in the turnover of the muscle small ankyrin-1 isoform 5 and, in combination with KCTD11, in the ubiquitination and degradation of HDAC1. The analyses show that the domain is a tetramer made up by subunits with the expected α/ structure. A detailed investigation of its stability, carried out in comparison with the homologous pentameric POZ/BTB domain isolated from KCTD5, highlights a number of interesting features, which are shared by the two domains despite their different organization. Their thermal/chemical denaturation curves are characterized by a single and sharp inflection point, suggesting that the denaturation of the two domains is a cooperative two-state process. Furthermore, both domains present a significant content of secondary structure in their denatured state and a reversible denaturation process. We suggest that the ability of these domains to fold and unfold reversibly, a property that is somewhat unexpected for these oligomeric assemblies, may have important implications for their biological function. Indeed, these properties likely favor the formation of heteromeric associations that may be essential for the intricate regulation of the processes in which these proteins are involved.