Subunit-dependent assembly of inward-rectifier K+ channels.
Inward-rectifier, G-protein-regulated and ATP-dependent K+ channels form a novel gene family of related proteins which share two transmembrane segments as a common structural feature. These K+ channels are only distantly related to the voltage-gated Shaker-type K+ channels comprising six transmembrane segments. Although the quaternary structure of voltage-gated K+ channels has been extensively studied in the past, little is known about subunit assembly of inward-rectifier K+ channels. Differential sensitivity of inward-rectifier K+ channels to voltage-dependent pore block by spermine was used to analyse subunit assembly. It is shown that inward-rectifier K+ channel proteins are composed of four subunits whose assembly obeys the rules of a binomial distribution. 'Strong' and 'mild' inward-rectifier K+ channel subunits (BIR10 and ROMK1) which are co-expressed in individual auditory hair cells form hetero-tetramers. Distribution of these hetero-tetramers, however, is not binomial. Hetero- and homo-oligomeric channels form with similar probabilities resulting in independent channel populations with distinct functional properties.
Glowatzki
E
E
Department of Sensory Biophysics, ENT-Hospital of the University of Tübingen, Germany.
Fakler
G
G
Brändle
U
U
Rexhausen
U
U
Zenner
H P
HP
Ruppersberg
J P
JP
Fakler
B
B
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D018072:Hair Cells, Auditory, Outer / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014981:Xenopus
D017931:DNA Primers; D015221:Potassium Channels; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins