Chlorella virus ATCV-1 encodes a functional potassium channel of 82 amino acids.
Chlorella virus PBCV-1 (Paramecium bursaria chlorella virus-1) encodes the smallest protein (94 amino acids, named Kcv) previously known to form a functional K+ channel in heterologous systems. In this paper, 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 cerevisiae mutants that lack endogenous K+ uptake systems. Compared with 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 caesium. Single channel analyses reveal a stochastic gating behaviour 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 tyrosine residue in the selective filter of ATCV-1 Kcv, whereas PBCV-1 Kcv has a phenylalanine. 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.
Gazzarrini
Sabrina
S
Department of Biology and CNR - Istituto di Biofisica, Università degli Studi di Milano, Italy.
Kang
Ming
M
Abenavoli
Alessandra
A
Romani
Giulia
G
Olivari
Claudio
C
Gaslini
Daniele
D
Ferrara
Giuseppina
G
van Etten
James L
JL
Kreim
Michael
M
Kast
Stefan M
SM
Thiel
Gerhard
G
Moroni
Anna
A
D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000494:pharmacology; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology; D002708:Chlorella / Q000821:virology*; D005260:Female; D005816:Genetic Complementation Test; D017136:Ion Transport; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014982:Xenopus laevis
D027682:Cation Transport Proteins; C405463:Kcv potassium channel, Chlorella virus; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D029701:Saccharomyces cerevisiae Proteins; C085258:TRK2 protein, S cerevisiae; D014764:Viral Proteins; C068664:TRK1 protein, S cerevisiae; D001464:Barium; D011188:Potassium