Fission yeast and a plant have functional homologues of the Sar1 and Sec12 proteins involved in ER to Golgi traffic in budding yeast

• Published in: The EMBO journal Vol. 11; no. 11; pp. 4205 - 4211
• Main Authors: d'Enfert, C., Gensse, M., Gaillardin, C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.11.1992
• Subjects: Amino Acid Sequence; amino acid sequences; Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; binding proteins; Biological and medical sciences; cDNA; complementary DNA; complementation; DNA; DNA - genetics; DNA - isolation & purification; DNA, Fungal; DNA, Fungal - genetics; DNA, Fungal - isolation & purification; endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Fundamental and applied biological sciences. Psychology; Fungal Proteins; Fungal Proteins - genetics; Fungal Proteins - metabolism; Gene Library; genes; Genes, Fungal; Genes, Lethal; Genes. Genome; Genetic Complementation Test; genetics; Golgi apparatus; Golgi Apparatus - metabolism; GTP-Binding Proteins; GTP-Binding Proteins - genetics; GTP-Binding Proteins - metabolism; Guanine Nucleotide Exchange Factors; guanosine triphosphate; isolation & purification; Membrane Glycoproteins; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; membrane proteins; metabolism; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Monomeric GTP-Binding Proteins; nucleotide sequence; nucleotide sequences; plant proteins; predictions; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; Sar1p protein; Schizosaccharomyces; Schizosaccharomyces - genetics; Schizosaccharomyces - metabolism; Schizosaccharomyces pombe; Sec12p protein; secretion; Sequence Homology, Amino Acid; structural genes; Vesicular Transport Proteins; Intracellular transport; GTP; Membrane protein; Yeast; Homology; Primary structure; Biological activity; Fungi; Arabidopsis thaliana; Binding protein; Complementary DNA; Cruciferae; Dicotyledones; Angiospermae; Schizosaccharomyces pombe; Ascomycetes; Spermatophyta; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1992.tb05514.x

Sec12p and Sar1p are required for the formation of transport vesicles generated from the endoplasmic reticulum (ER) in the yeast Saccharomyces cerevisiae. Sec12p is an ER type II membrane protein that mediates the membrane attachment of the GTP‐binding Sar1 protein. The SAR1 gene is a multi‐copy suppressor of a thermosensitive sec12 mutation. In an attempt to identify functional homologues of Sec12p and Sar1p from other eukaryotic organisms, we screened cDNA expression libraries derived from the fission yeast Schizosaccharomyces pombe and from the plant Arabidopsis thaliana for complementation of the sec12ts mutation. Four individual cDNAs were isolated, two of which encode the S. pombe and A. thaliana homologues of Sar1p. The three Sar1 proteins are 67% identical on average. The two other cDNAs encode type II membrane proteins which were designated Stl1p for the S. pombe protein and Stl2p for the A. thaliana protein (Stl stands for Sec12p‐like). Both proteins have NH2‐terminal cytoplasmic domains which resemble that of Sec12p: they are similar in size and present a significant degree of amino acid identity with the cytoplasmic domain of Sec12p. In contrast, the lumenal domains of Sec12p, Stl1p and Stl2p are very different in size and do not show any appreciable homology. That Stl1p and Stl2p are functional homologues of Sec12p was confirmed by showing that expression of either cloned gene complements a sec12 null mutation. Our results indicate that some of the mechanisms regulating vesicle formation at the ER are conserved not only in yeasts, but also in plants.