Abstract

A cluster of genes encoding the pyruvate dehydrogenase complex (PDC) of Streptomyces seoulensis, a Gram-positive bacterium, was cloned and sequenced. The genes of S. seoulensis consist of four open reading frames. The first gene, lpd, which encodes a lipoamide dehydrogenase, is followed by pdhB encoding a dihydrolipoamide acetyltransferase (E2p), pdhR, a regulatory gene, and pdhA encoding a pyruvate dehydrogenase component (E1p). E1p had an unusual homodimeric subunit, which has been known only in Gram-negative bacteria. S. seoulensis E2p contains two lipoyl domains like those of humans and Streptococcus faecalis. The pdhR gene appears to be clustered with the structural genes of S. seoulensis PDC. The PdhR-overexpressed S. seoulensis showed growth retardation and the decrease of E1p, indicating that PdhR regulates the function of PDC by repressing the expression of E1p. A strain of Streptomyces lividans overexpressing S. seoulensis PdhR showed a significant decrease in the level of actinorhodin, implying a regulatory role for Streptomyces PDC in antibiotic biosynthesis.

• Keywords: pyruvate dehydrogenase; dihydrolipoamide acetyltransferase; lipoamide dehydrogenase; PdhR; actinorho