Chlorella virus ATCV1 encodes a functional potassium channel of eighty-two amino acids

Sabrina Gazzarrini , Ming Kang , Alessandra Abenavoli , Giulia Romani , Claudio Olivari , Daniele Gaslini , Giuseppina Ferrara , James L. van Etten , Michael Kreim , Stefan M. Kast , Gerhard Thiel , Anna Moroni (1)

1 Dipartimento di Biologia

Chlorella virus PBCV-1 encodes the smallest protein (94 amino acids, named Kcv) previously known to form a functional K+ channel in heterologous systems. In the current manuscript, we characterize another chlorella virus encoded K+ channel protein (82 amino acids, named ATCV-1 Kcv) that forms a functional channel in Xenopus oocytes and rescues Saccharomyces cerevisae mutants that lack endogenous K+ uptake systems. Compared to the larger PBCV-1 Kcv, ATCV-1 Kcv lacks a cytoplasmic N-terminus and has a reduced number of charged amino acids in its turret domain. Despite these deficiencies, ATCV-1 Kcv accomplishes all the major features of K+ channels: it assembles into a tetramer, is K+ selective and is inhibited by the canonical K+ channel blockers, barium and cesium. Single channel analyses reveal a stochastic gating behavior and a voltage-dependent conductance that resembles the macroscopic I/V relationship. One difference between PBCV-1 and ATCV-1 Kcv is that the latter is more permeable to K+ than Rb+. This difference is partially explained by the presence of a Tyr residue in the selective filter of ATCV-1 Kcv, whereas PBCV-1 Kcv has a Phe. Hence, ATCV-1 Kcv is the smallest protein to form a K+ channel and it will serve as a model for studying structure/function correlations inside the potassium channel pore.

Mots clés: Life Sciences

Sabrina Gazzarrini, Ming Kang, Alessandra Abenavoli, Giulia Romani, Claudio Olivari, et al.. Chlorella virus ATCV1 encodes a functional potassium channel of eighty-two amino acids. Biochemical Journal, 2009, 420 (2), pp.295-303. ⟨10.1042/BJ20090095⟩. ⟨hal-00479153⟩