Efficient ER exit and vacuole targeting of yeast Sna2p require two tyrosine-based sorting motifs.
SNA (Sensitive to Na(+)) proteins form a membrane protein family, which, in the yeast Saccharomyces cerevisiae, is composed of four members: Sna1p/Pmp3p, Sna2p, Sna3p and Sna4p. In this study, we focused on the 79 residue Sna2p protein. We found that Sna2p is localized in the vacuolar membrane. Directed mutagenesis showed that two functional tyrosine motifs YXXØ are present in the C-terminal region. Each of these is involved in a different Golgi-to-vacuole targeting pathway: the tyrosine 65 motif is involved in adaptor protein (AP-1)-dependent targeting, whereas the tyrosine 75 motif is involved in AP-3-dependent targeting. Moreover, our data suggest that these motifs also play a crucial role in the exit of Sna2p from the endoplasmic reticulum (ER). Directed mutagenesis of these tyrosines led to a partial redirection of Sna2p to lipid bodies, probably because of a decrease in ER exit efficiency. Sna2p is the first yeast protein in which two YXXØ motifs have been identified and both were shown to be functional at two different steps of the secretory pathway, ER exit and Golgi-to-vacuole transport.
Renard
Henri-François
HF
Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4/15, B-1348 Louvain-la-Neuve, Belgium.
Demaegd
Didier
D
Guerriat
Bérengère
B
Morsomme
Pierre
P
D020816:Amino Acid Motifs; D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism*; D015003:Yeasts
D005656:Fungal Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C555105:Sna2 protein, S cerevisiae; D018808:Transcription Factor AP-1; D050988:Vesicle-Associated Membrane Protein 2; D014443:Tyrosine