A. Rodriguezgarcia et al., ARGININE BOXES AND THE ARGR GENE IN STREPTOMYCES-CLAVULIGERUS - EVIDENCE FOR A CLEAR REGULATION OF THE ARGININE PATHWAY, Molecular microbiology, 25(2), 1997, pp. 219-228
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.