Streptomyces coelicolor is the soil-dwelling bacterium with a complex life cycle and a strong ability to produce plenty of secondary metabolites which are strictly regulated by a variety of regulators. Amino acid alignment shows that the deduced protein of SCO2140 belongs to the family of Leucine-responsive regulatory proteins (Lrps). Disruption of SCO2140 significantly decreased the yields of actinorhodin and calcium-dependent antibiotics, and the complemented strain restored the antibiotic productions to the wild-type level. In contrast, overexpression of SCO2140 increased the actinorhodin production. In agreement with it, the transcriptions of actII-ORF4 and cdaR remarkably reduced in the SCO2140 disruption mutant. The aerial mycelium formation of the SCO2140 disruption mutant was clearly delayed in R2YE medium due to the decrease of ramS expression while its complemented strain could restore the normal formation of aerial mycelia. These results indicated that SCO2140 was involved in antibiotic biosynthesis and morphological differentiation of Streptomyces coelicolor A3(2).