A PP2C-type phosphatase dephosphorylates the PII signaling protein in the cyanobacterium Synechocystis PCC 6803
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
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Edited by Sydney Kustu, University of California, Berkeley, CA, and approved August 15, 2001 (received for review May 22, 2001)
Abstract
The family of the PII signal transduction proteins contains the most highly conserved signaling proteins in nature. The cyanobacterial PII-homologue transmits signals of the cellular nitrogen status and carbon status through phosphorylation of a seryl-residue. To identify the enzyme responsible for dephosphorylation of the phosphorylated PII protein in Synechocystis PCC 6803, prospective phosphatase encoding genes were inactivated by targeted insertion of kanamycin resistance cassettes. Disruption of ORF sll1771 generates a mutant unable to dephosphorylate PII under various experimental conditions. On the basis of conserved signature motifs, the sll1771 product (termed PphA) is a member of the protein phosphatase 2C (PP2C) superfamily, which is characterized by Mg2+/Mn2+-dependent catalytic activity. Biochemical analysis of overexpressed and purified PphA confirms its PP2C-type enzymatic properties and demonstrated its reactivity toward the phosphorylated PII protein. Thus, PphA is the first protein phosphatase in Synechocystis PCC 6803 for which the physiological substrate and function is known.
Footnotes
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↵ * To whom reprint requests should be addressed. E-mail: karl.forchhammer{at}mikro.bio.uni-giessen.de.
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This paper was submitted directly (Track II) to the PNAS office.
- Abbreviation:
- PP,
- protein phosphatases
- Copyright © 2001, The National Academy of Sciences
