ARGININE BOXES AND THE ARGR GENE IN STREPTOMYCES-CLAVULIGERUS - EVIDENCE FOR A CLEAR REGULATION OF THE ARGININE PATHWAY

The argR gene of Streptomyces clavuligerus has been located in the ups tream region of argG. It encodes a protein of 160 amino acids with a d educed M-r of 17117 for the monomer. Transformants containing the ampl ified argR gene showed lower activity (50%) of the biosynthetic ornith ine carbamoyltransferase (OTC) activity and higher levels (380%) of th e catabolic ornithine aminotransferase (OAT) activity than control str ains. Amplification of an arginine (ARG) box-containing sequence resul ts in a 2- to 2.5-fold derepression of ornithine acetyltransferase and OTC, suggesting that the repressor is titrated out. Footprinting expe riments using the pure homologous arginine repressor (AhrC) of B. subt ilis showed a protected 38 nt region (ARG box) in the coding strand up stream of argC. The protected region contained two tandemly repeated i mperfect palindromic 18-nt ARG boxes. The repressor-operator interacti on was confirmed by bandshift experiments of the DNA fragment containi ng the protected region. By computer analysis of the Streptomyces sequ ences available in the databases, a consensus ARG box has been deduced for the genus Streptomyces. This is the first example of a clear regu lation of an amino acid biosynthetic pathway in Streptomyces species, challenging the belief that actinomycetes do not have a well-developed regulatory system of these pathways.