title: Functional analysis of domains in the Byr2 kinase.
abstract: The activation of mitogen-activated protein (MAP) kinase cascades by the Ras GTPase is an evolutionarily conserved signal transduction mechanism. To better understand the interaction between Ras and its target kinase, we study the yeast Schizosaccharomyces pombe where the Ras1 GTPase activates the Byr2 kinase. The Byr2 kinase contains an N-terminal regulatory region and a C-terminal kinase region. The regulatory region can be divided into a sterile-alpha motif (SAM) that binds Ste4, a Ras1-binding domain (RBD) that binds activated Ras1, and a catalytic binding domain (CBD) that interacts with the Byr2 kinase domain. To analyze the importance of functional domains of the Byr2 kinase, a biological assay was used that exploited the ability of Byr2 to partially bypass the need for Ras1 in sporulation. Analysis of mutants using this assay showed that SAM and RBD were very important for Ras1-stimulated sporulation. Three activating mutations were identified within the N-terminal lobe of the Byr2 kinase domain that partially bypassed the need for Ras1 for sporulation. These activating mutations may identify a region of the Byr2 kinase domain that interacts with the CBD since mutations in the CBD which disrupt binding to the kinase domain also increase Byr2 function.
authors.affiliation: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.
authors.forename: P
authors.initials: P
authors.lastname: Bauman
authors.forename: C F
authors.initials: CF
authors.lastname: Albright
mesh_terms: D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits; D019204:GTP-Binding Proteins / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins; D020930:MAP Kinase Kinase Kinases; D009154:Mutation; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D017384:Sequence Deletion; D018631:ras Proteins / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D044387:GTP-Binding Protein beta Subunits; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C067576:Ste4 protein, S cerevisiae; D011494:Protein Kinases; 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