title: Regions of Byr4, a regulator of septation in fission yeast, that bind Spg1 or Cdc16 and form a two-component GTPase-activating protein with Cdc16.
abstract: In the fission yeast Schizosaccharomyces pombe, septation and constriction of the actomyosin ring for cell division are positively regulated by the Spg1 GTPase, a member of the Ras superfamily. Spg1 is negatively regulated by Byr4 and Cdc16, which together form a two-component GTPase-activating protein for the Spg1 GTPase. To better understand how Byr4 regulates septation, Byr4 mutants were tested for in vitro functions. This analysis revealed that Byr4 contained one Cdc16-binding site and four Spg1-binding sites (SBS), designated SBS1-SBS4. Although mutants with a single SBS bound Spg1 and inhibited GTP dissociation, the equilibrium binding affinity of these mutants was 28-280-fold weaker than Byr4. Because some Byr4 mutants with multiple SBSs bound Spg1 tighter than the corresponding mutants with a single SBS, multiple SBSs probably interact to cause the high affinity binding of Byr4 to Spg1. A region of Byr4 that bound Spg1, SBS4, and the region that bound Cdc16, Cdc16-binding site, was necessary and sufficient to form Cdc16-dependent Spg1GAP activity that was similar to that of wild-type Byr4 with Cdc16.
authors: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors: K A
authors: KA
authors: Furge
authors: Q C
authors: QC
authors: Cheng
authors: M
authors: M
authors: Jwa
authors: S
authors: S
authors: Shin
authors: K
authors: K
authors: Song
authors: C F
authors: CF
authors: Albright
mesh_terms: D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D009154:Mutation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D012097:Repressor Proteins; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D020703:ras GTPase-Activating Proteins
chemical_list: C100413:Byr4 protein, S pombe; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D011506:Proteins; D012097:Repressor Proteins; D029702:Schizosaccharomyces pombe Proteins; C498281:cdc16 protein, S pombe; D020703:ras GTPase-Activating Proteins; D020558:GTP Phosphohydrolases