N-terminal domain of Streptomyces griseus SgaA and similar domains
SgaA suppresses the growth disturbances caused by high osmolarity and a high concentration of A-factor, a microbial hormone, during the early growth phase in Streptomyces griseus. A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) controls morphological differentiation and secondary metabolism in Streptomyces griseus. It is a chemical signaling molecule that at a very low concentration acts as a switch for yellow pigment production, aerial mycelium formation, streptomycin production, and streptomycin resistance. The structure and amino acid sequence of SgaA are closely related to a group of antibiotics resistance proteins, including bleomycin resistance protein, mitomycin resistance protein, and fosfomycin resistance proteins. SgaA might also function as a streptomycin resistance protein.