Polyphosphate kinase 1, a conserved bacterial enzyme, in a eukaryote, Dictyostelium discoideum, with a role in cytokinesis

Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307

Contributed by Arthur Kornberg, July 20, 2007 (received for review May 16, 2007)

Abstract

Polyphosphate kinase 1 (PPK1), the principal enzyme responsible for reversible synthesis of polyphosphate (poly P) from the terminal phosphate of ATP, is highly conserved in bacteria and archaea. Dictyostelium discoideum, a social slime mold, is one of a few eukaryotes known to possess a PPK1 homolog (DdPPK1). Compared with PPK1 of Escherichia coli, DdPPK1 contains the conserved residues for ATP binding and autophosphorylation, but has an N-terminal extension of 370 aa, lacking homology with any known protein. Polyphosphate or ATP promote oligomerization of the enzyme in vitro. The DdPPK1 products are heterogeneous in chain length and shorter than those of E. coli. The unique DdPPK1 N-terminal domain was shown to be necessary for its enzymatic activity, cellular localization, and physiological functions. Mutants of DdPPK1, as previously reported, are defective in development, sporulation, and predation, and as shown here, in late stages of cytokinesis and cell division.

Footnotes

^‡To whom correspondence should be addressed at:
Department of Biochemistry, Stanford University School of Medicine, B415 Beckman Center, 279 Campus Drive West, Stanford, CA 94305-5307.
E-mail: akornber{at}cmgm.stanford.edu
Author contributions: H.Z., M.R.G.-G., X.S., N.N.R., and A.K. designed research; H.Z., M.R.G.-G., and X.S. performed research; N.N.R. contributed new reagents/analytic tools; H.Z., M.R.G.-G., X.S., N.N.R., and A.K. analyzed data; and H.Z., M.R.G.-G., X.S., N.N.R., and A.K. wrote the paper.
↵*Present address: Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305.
↵ ^†Present address: Department of Biological Sciences, Stanford University, Stanford, CA 94305.
The authors declare no conflict of interest.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF176830).
This article contains supporting information online at www.pnas.org/cgi/content/full/0706847104/DC1.
Abbreviations:

poly P,

inorganic polyphosphate;

PPK,

polyphosphate kinase;

DdPPK1,

Dictyostelium discoideum PPK1;

EcPPK1,

Escherichia coli PPK1;

Pi,

orthophosphate.