Interactions of three domains distinguishing the Ras-related GTP-binding proteins Ypt1 and Sec4.
The genes SEC4 and YPT1 encode Ras-related GTP-binding proteins in the yeast Saccharomyces cerevisiae. Ypt1 is necessary for vesicular transport from the endoplasmic reticulum to the Golgi, whereas Sec4 is required for fusion of post-Golgi secretory vesicles to the plasma membrane. Recently, three structural domains have been proposed to specify the stage in cellular transport at which members of the Sec4/Ypt1/Rab family act: the effector domain, the C-terminal hypervariable region, and a region corresponding to loop 7 in the structure of p21ras (ref. 8). Here we use Sec4/Ypt1 chimaeras to show that these three regions cooperate to specify Ypt1 function and that the C-terminal hypervariable region is needed for Ypt1 localization to the Golgi. Unexpectedly, we found that a single chimaera can function as either Ypt1 or Sec4 without missorting carboxypeptidase Y or invertase.
Brennwald
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Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
Novick
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D000595:Amino Acid Sequence; D002268:Carboxypeptidases / Q000378:metabolism; D043402:Cathepsin A; D004252:DNA Mutational Analysis; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000737:chemistry; D019204:GTP-Binding Proteins / Q000737:chemistry*; D006026:Glycoside Hydrolases / Q000378:metabolism; D006056:Golgi Apparatus / Q000737:chemistry; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins; D043324:beta-Fructofuranosidase; D020691:rab GTP-Binding Proteins
D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D002268:Carboxypeptidases; D043402:Cathepsin A; C499283:PRC1 protein, S cerevisiae; C022633:serine carboxypeptidase; D019204:GTP-Binding Proteins; C060755:YPT1 protein, S cerevisiae; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins