The BTB domains of the potassium channel tetramerization domain proteins prevalently assume pentameric states

FEBS Lett. 2016 Jun;590(11):1663-71. doi: 10.1002/1873-3468.12203.

Giovanni Smaldone ¹, Luciano Pirone ² ³, Emilia Pedone ², Thomas Marlovits ⁴ ⁵ ⁶ ⁷, Luigi Vitagliano ², Luciano Ciccarelli ⁴ ⁵ ⁶ ⁷

Affiliations

1 IRCCS SDN, Napoli, Italy.
2 Institute of Biostructures and Bioimaging, C.N.R., Napoli, Italy.
3 Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.), Catania, Italy.
4 Center for Structural Systems Biology (CSSB), University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany.
5 Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany.
6 Institute of Molecular Biotechnology (IMBA), Austrian Academy of Sciences, Vienna, Austria.
7 Research Institute of Molecular Pathology (IMP), Vienna, Austria.

PMID: 27152988 DOI: 10.1002/1873-3468.12203

Abstract

Potassium Channel tetramerization domain-containing (KCTD) proteins are involved in fundamental physio-pathological processes. Here, we report an analysis of the oligomeric state of the Bric-à-brack, Tram-track, Broad complex (BTB) domains of seven distinct KCTDs belonging to five major clades of the family evolution tree. Despite their functional and sequence variability, present electron microscopy data highlight the occurrence of well-defined pentameric states for all domains. Our data also show that these states coexist with alternative forms which include open pentamers. Thermal denaturation analyses conducted using KCTD1 as a model suggest that, in these proteins, different domains cooperate to their overall stability. Finally, negative-stain electron micrographs of KCTD6(BTB) in complex with Cullin3 show the presence of assemblies with a five-pointed pinwheel shape.

Keywords

electron microscopy; protein oligomerization; protein structure; thermal stability.

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