THE CLAR GENE OF STREPTOMYCES-CLAVULIGERUS, ENCODING A LYSR-TYPE REGULATORY PROTEIN CONTROLLING CLAVULANIC ACID BIOSYNTHESIS, IS LINKED TO THE CLAVULANATE-9-ALDEHYDE REDUCTASE (CAR) GENE
R. Perezredondo et al., THE CLAR GENE OF STREPTOMYCES-CLAVULIGERUS, ENCODING A LYSR-TYPE REGULATORY PROTEIN CONTROLLING CLAVULANIC ACID BIOSYNTHESIS, IS LINKED TO THE CLAVULANATE-9-ALDEHYDE REDUCTASE (CAR) GENE, Gene, 211(2), 1998, pp. 311-321
Two genes, claR and car, encoding proteins involved in clavulanic acid
biosynthesis, have been found in a 2.8-kb BglII-EcoRI DNA fragment of
Streptomyces clavuligerus adjacent to the region containing the cepha
mycin and clavulanic acid biosynthesis gene cluster. claR encoded a pr
otein of 431 amino acids (deduced M-r 47 080), that showed a significa
nt degree of homology with several transcriptional activators of the L
ysR family. The ClaR protein contained two helix-turn-helix (HTH) moti
fs in the amino and carboxyl terminal regions. The second gene, car, e
ncoded a protein of 247 amino acids (M-r 26 629) that showed a strong
similarity to oxydoreductases of the SDR family. Twelve amino acids of
the amino-terminal region were identical to those previously obtained
by Edman degradation of the purified clavulanic-9-aldehyde reductase
of S. clavuligerus. Amplification of the claR gene in multicopy plasmi
ds resulted in a threefold increase in clavulanic acid production and
in a five- to sixfold increase of alanylclavam biosynthesis, whereas c
ephamycin production was significantly reduced both in defined and in
complex media. By contrast, amplification of the car gene had no signi
ficant effect on clavulanic acid and alanylclavam or cephamycin produc
tion. Both claR and car are expressed as monocistronic transcripts; th
e level of transcript declined rapidly after 48 h in complex media, bu
t low sustained levels of both transcripts were observed in defined GS
PG medium until 96 h. claR and car were not significantly expressed in
mutants disrupted in the ccaR gene, a regulatory gene that controls p
ositively clavulanic acid and cephamycin biosynthesis. These results i
ndicate that clavulanic acid and cephamycin biosynthesis in S. clavuli
gerus is controlled by a cascade of regulatory proteins that include C
caR and ClaR. (C) 1998 Elsevier Science B.V. All rights reserved.