Transmembrane domain length of viral K+ channels is a signal for mitochondria targeting.
K(+) channels operate in the plasma membrane and in membranes of organelles including mitochondria. The mechanisms and topogenic information for their differential synthesis and targeting is unknown. This article describes 2 similar viral K(+) channels that are differentially sorted; one protein (Kesv) is imported by the Tom complex into the mitochondria, the other (Kcv) to the plasma membrane. By creating chimeras we discovered that mitochondrial sorting of Kesv depends on a hierarchical combination of N- and C-terminal signals. Crucial is the length of the second transmembrane domain; extending its C terminus by > or = 2 hydrophobic amino acids redirects Kesv from the mitochondrial to the plasma membrane. Activity of Kesv in the plasma membrane is detected electrically or by yeast rescue assays only after this shift in sorting. Hence only minor structural alterations in a transmembrane domain are sufficient to switch sorting of a K(+) channel between the plasma membrane and mitochondria.
Balss
Jörg
J
Institute of Botany, Technische Universität Darmstadt, D-64287 Darmstadt, Germany.
Papatheodorou
Panagiotis
P
Mehmel
Mario
M
Baumeister
Dirk
D
Hertel
Brigitte
B
Delaroque
Nicolas
N
Chatelain
Franck C
FC
Minor
Daniel L
DL
Van Etten
James L
JL
Rassow
Joachim
J
Moroni
Anna
A
Thiel
Gerhard
G
D000595:Amino Acid Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins; D008928:Mitochondria / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D017862:Phycodnaviridae / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D021382:Protein Sorting Signals; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
D008565:Membrane Proteins; D015221:Potassium Channels; D021382:Protein Sorting Signals; D014764:Viral Proteins