Multiple regulatory domains on the Byr2 protein kinase.
Byr2 protein kinase, a homolog of mammalian mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEKK) and Saccharomyces cerevisiae STE11, is required for pheromone-induced sexual differentiation in the fission yeast Schizosaccharomyces pombe. Byr2 functions downstream of Ste4, Ras1, and the membrane-associated receptor-coupled heterotrimeric G-protein alpha subunit, Gpa1. Byr2 has a distinctive N-terminal kinase regulatory domain and a characteristic C-terminal kinase catalytic domain. Ste4 and Ras1 interact with the regulatory domain of Byr2 directly. Here, we define the domains of Byr2 that bind Ste4 and Ras1 and show that the Byr2 regulatory domain binds to the catalytic domain in the two-hybrid system. Using Byr2 mutants, we demonstrate that these direct physical interactions are all required for proper signaling. In particular, the physical association between Byr2 regulatory and catalytic domains appears to result in autoinhibition, the loss of which results in kinase activation. Furthermore, we provide evidence that Shk1, the S. pombe homolog of the STE20 protein kinase, can directly antagonize the Byr2 intramolecular interaction, possibly by phosphorylating Byr2.
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Cold Spring Harbor Laboratory, New York 11724, USA.
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Dong
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Wigler
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D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits; D019204:GTP-Binding Proteins / Q000378:metabolism; D005800:Genes, Fungal / Q000235:genetics; D020962:Heterotrimeric GTP-Binding Proteins; D020930:MAP Kinase Kinase Kinases; D017354:Point Mutation; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D029702:Schizosaccharomyces pombe Proteins; D013172:Spores, Fungal; D054462:p21-Activated Kinases; D018631:ras Proteins / Q000378:metabolism
D005656:Fungal Proteins; D044387:GTP-Binding Protein beta Subunits; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C067576:Ste4 protein, S cerevisiae; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; C094341:shk1 protein, S pombe; C077892:BYR2 protein, S pombe; D020930:MAP Kinase Kinase Kinases; D019204:GTP-Binding Proteins; D020962:Heterotrimeric GTP-Binding Proteins; C489014:RAS1 protein, S cerevisiae; C492657:Ras1 protein, S pombe; D018631:ras Proteins