Transcription of <i>ppk</i> from <i>Acinetobacter</i> sp. Strain ADP1, Encoding a Putative Polyphosphate Kinase, Is Induced by Phosphate Starvation

Abstract

Polyphosphate kinase (Ppk) catalyzes the formation of polyphosphate from ATP. We cloned the ppk gene (2,073 bp) from Acinetobacter sp. strain ADP1; this gene encodes a putative polypeptide of 78.6 kDa with extensive homology to polyphosphate kinase from Escherichia coli and other bacteria. Chromosomal disruption of ppk by inserting a transcriptionally fused lacZ does not affect growth under conditions of phosphate limitation or excess. beta-Galactosidase activity expressed from the single-copy ppk::lacZ fusion is induced 5- to 15-fold by phosphate starvation. An increased amount of ppk transcript (2.2 kb) was detected when cells were grown at a limiting phosphate concentration. Primer extension analysis revealed a regulated promoter located upstream of a second, constitutive promoter. Potential similarities of this regulation with the effects of PhoB and PhoR of E. coli are discussed.