ER export of KAT1 is correlated to the number of acidic residues within a triacidic motif.
For a number of ion channels, including the potassium (K(+)) inward rectifying channel from Arabidopsis thaliana (KAT1), diacidic endoplasmic reticulum (ER) export motifs have been identified. These motifs consist of two acidic amino acids (aspartate (D) and/or glutamate (E)) separated by any amino acid. To specify the role of single acidic amino acids for efficiency of ER export, we analysed a sequence of KAT1 that included the originally identified diacidic ER export motif (DxE) plus an additional D just upstream of the diacidic motif. Analysis of single, double and triple mutations of the acidic amino acids of the DxDxE motif revealed a gradual reduction of ER export depending on the number of mutated acidic residues. The amount of reduction in ER export was not related to the position, but only to the number of mutated acidic amino acids. These results show that a triacidic motif is essential for efficient ER export of KAT1. Function of the triacidic motif probably involves cooperative binding to Sec24.
Mikosch
Melanie
M
Institute of Botany, Technische Universität Darmstadt, Darmstadt, Germany.
Käberich
Katrin
K
Homann
Ulrike
U
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D024342:Amino Acids, Acidic / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000235:genetics / Q000378:metabolism; D022181:COP-Coated Vesicles / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014162:Transfection
D024342:Amino Acids, Acidic; D029681:Arabidopsis Proteins; C501210:KAT1 protein, Arabidopsis; D008565:Membrane Proteins; D024661:Potassium Channels, Inwardly Rectifying; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid