The yeast translational allosuppressor, SAL6: a new member of the PP1-like phosphatase family with a long serine-rich N-terminal extension.
The allosuppressor mutation, sal6-1, enhances the efficiency of all tested translational suppressors, including codon-specific tRNA suppressors as well as codon-nonspecific omnipotent suppressors. The SAL6 gene has now been cloned by complementation of the increased suppression efficiency and cold sensitivity caused by sal6-1 in the presence of the omnipotent suppressor sup45. Physical analysis maps SAL6 to chromosome XVI between TPK2 and spt14. The SAL6 gene encodes a very basic 549-amino acid protein whose C-terminal catalytic region of 265 residues is 63% identical to serine/threonine PP1 phosphatases, and 66% identical to yeast PPZ1 and PPZ2 phosphatases. The unusual 235 residue N-terminal extension found in SAL6, like those in the PPZ proteins, is serine-rich. The sal6-1 mutation is a frameshift at amino acid position 271 which destroys the presumed phosphatase catalytic domain of the protein. Disruptions of the entire SAL6 gene are viable, cause a slight growth defect on glycerol medium, and produce allosuppressor phenotypes in suppressor strain backgrounds. The role of the serine-rich N terminus is unclear, since sal6 phenotypes are fully complemented by a SAL6 allele that contains an in-frame deletion of most of this region. High copy number plasmids containing wild-type SAL6 cause antisuppressor phenotypes in suppressor strains. These results suggest that the accuracy of protein synthesis is affected by the levels of phosphorylation of the target(s) of SAL6.
Department of Biological Sciences, University of Illinois at Chicago 60680.
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Liebman
D000595:Amino Acid Sequence; D001483:Base Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D004271:DNA, Fungal; D015966:Gene Expression Regulation, Fungal; D016153:Genes, Suppressor; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D014176:Protein Biosynthesis; D054645:Protein Phosphatase 1; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000032:analysis / Q000235:genetics
D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D012694:Serine; C091992:PPQ1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1