Dominant mutations in a gene encoding a putative protein kinase (BCK1) bypass the requirement for a Saccharomyces cerevisiae protein kinase C homolog.
The PKC1 gene of Saccharomyces cerevisiae encodes a homolog of mammalian protein kinase C that is required for yeast cell growth and division. To identify additional components of the pathway in which PKC1 functions, we isolated extragenic suppressors of a pkc1 deletion mutant. All of the suppressor mutations were dominant for suppressor function and defined a single locus, which was designated BCK1 (for bypass of C kinase). A molecular clone of one suppressor allele, BCK1-20, was isolated on a centromere-containing plasmid through its ability to rescue a conditional pkc1 mutant. The BCK1 gene possesses a 4.4-kb uninterrupted open reading frame predicted to encode a 163-kDa protein kinase. The BCK1 gene product is not closely related to any known protein kinase, sharing only 45% amino acid identity with its closest known relative (the STE11-encoded protein kinase) through a region restricted to its putative C-terminal catalytic domain. Deletion of BCK1 resulted in a temperature-sensitive cell lysis defect, which was suppressed by osmotic stabilizing agents. Because pkc1 mutants also display a cell lysis defect, we suggest that PKC1 and BCK1 may normally function within the same pathway. Suppressor alleles of BCK1 differed from the wild-type gene in a region surrounding a potential PKC phosphorylation site immediately upstream of the predicted catalytic domain. This region may serve as a hinge between domains whose interaction is regulated by PKC1.
Lee
K S
KS
Department of Biochemistry, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
Levin
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DE
D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D004271:DNA, Fungal; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005799:Genes, Dominant; D005800:Genes, Fungal; D016153:Genes, Suppressor; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D011493:Protein Kinase C / Q000235:genetics* / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D013696:Temperature
D004271:DNA, Fungal; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; C072075:BCK1 protein, S cerevisiae; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases