Abstract
The
ppk
gene of
Streptomyces lividans
encodes an enzyme catalyzing, in vitro, the reversible polymerization of the γ phosphate of ATP into polyphosphate and was previously shown to play a negative role in the control of antibiotic biosynthesis (H. Chouayekh and M. J. Virolle, Mol. Microbiol.
43:
919-930, 2002). In the present work, some regulatory features of the expression of
ppk
were established and the polyphosphate content of
S. lividans
TK24 and the
ppk
mutant was determined. In P
i
sufficiency, the expression of
ppk
was shown to be low but detectable. DNA gel shift experiments suggested that
ppk
expression might be controlled by a repressor using ATP as a corepressor. Under these conditions, short acid-soluble polyphosphates accumulated upon entry into the stationary phase in the wild-type strain but not in the
ppk
mutant strain. The expression of
ppk
under P
i
-limiting conditions was shown to be much higher than that under P
i
-sufficient conditions and was under positive control of the two-component system PhoR/PhoP. Under these conditions, the polyphosphate content of the cell was low and polyphosphates were reproducibly found to be longer and more abundant in the
ppk
mutant strain than in the wild-type strain, suggesting that Ppk might act as a nucleoside diphosphate kinase. In light of our results, a novel view of the role of this enzyme in the regulation of antibiotic biosynthesis in
S. lividans
TK24 is proposed.