An essential GTP-binding protein functions as a regulator for differentiation in Streptomyces coelicolor.
The Streptomyces coelicolor obg gene, which encodes a putative GTP-binding protein of the Obg/Gtp1 family, was characterized. The obg gene was essential for viability. Introduction of multiple copies of obg into wild-type S. coelicolor suppressed aerial mycelium formation. A single amino acid substitution at any of six positions was introduced into the GTP binding site of Obg, and the mutated proteins were expressed in wild-type cells. Obg(P168-->V) exerted a more accentuated suppressive effect on aerial mycelium formation than did the wild-type Obg protein. In contrast, Obg(G171-->A) accelerated the development of aerial mycelium. These results show that Obg protein functions as a pivotal regulator for the onset of cell differentiation through its ability to bind GTP. Western analysis revealed that expression of obg is regulated in a growth phase-dependent manner, indicating a sharp decrease just after onset of aerial mycelium development or at the end of vegetative growth. Obg was a membrane-bound protein as determined by immunoelectron microscopy.
Okamoto
S
S
National Food Research Institute, Tsukuba, Ibaraki, Japan.
Ochi
K
K
D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D019204:GTP-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006160:Guanosine Triphosphate / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D016297:Mutagenesis, Site-Directed; D020161:Physical Chromosome Mapping; D011995:Recombination, Genetic; D013302:Streptomyces / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
D001426:Bacterial Proteins; C090542:Obg GTP-binding protein, Bacteria; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins