RraAS1 inhibits the ribonucleolytic activity of RNase ES by interacting with its catalytic domain in Streptomyces coelicolor.

RraA is a protein inhibitor of RNase E, which degrades and processes numerous RNAs in Escherichia coli. Streptomyces coelicolor also contains homologs of RNase E and RraA, RNase ES and RraAS1/RraAS2, respectively. Here, we report that, unlike other RraA homologs, RraAS1 directly interacts with the catalytic domain of RNase ES to exert its inhibitory effect. We further show that rraAS1 gene deletion in S. coelicolor results in a higher growth rate and increased production of actinorhodin and undecylprodigiosin, compared with the wild-type strain, suggesting that RraAS1-mediated regulation of RNase ES activity contributes to modulating the cellular physiology of S. coelicolor.