The 63-amino-acid-encoding afsR2 is a globalantibiotics-stimulating regulatory gene identified from thechromosome of Streptomyces lividans. To disect a putativefunctional domain in afsR2, several afsR2-derivative deletionconstructs were generated and screned for the los ofactinorhodin-stimulating capability. The afsR2-derivativeconstruct mising a 50-bp C-terminal region significantly lostits actinorhodin-stimulating capability in S. lividans. Inadition, site-directed mutagenesis on amino acid positions of#57-#61 in a 50-bp C-terminal region, some of which areconserved among known Sigma 70 family proteins, significantlychanged the AfsR2’s activity. These results imply that theC-terminal region of AfsR2 is functionally important forantibiotics-stimulating capability and the regulatory mechanismmight be somehow related to the sigma-like domain presentin the C-terminal of AfsR2.