Formation of an actin-like filament concurrent with the enzymatic synthesis of inorganic polyphosphate
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Contributed by Arthur Kornberg, September 17, 2004
Abstract
Inorganic polyphosphate (poly P), a chain of hundreds of phosphate residues linked by ATP-like bonds, is found in every cell in nature and is commonly produced from ATP by poly P kinases (e.g., PPK1). Dictyostelium discoideum, the social slime mold, possesses a PPK activity (DdPPK1) with sequence similarity to bacterial PPKs. We find here a previously unrecognized PPK (DdPPK2) in D. discoideum with the sequences and properties of actin-related proteins (Arps) that are similar to muscle actins in size, properties, and globular-filamentous structural transitions. Significantly, the unique actin inhibitors, phalloidin and DNase I, also inhibit synthesis of poly P by DdPPK2. Thus, this particular Arp complex is an enzyme that can polymerize into an actin-like filament concurrent with its synthesis of a poly P chain in a fully reversible reaction.
Footnotes
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↵ * 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.
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Abbreviations: Arp, actin-related protein; poly P, inorganic polyphosphate; PPK, poly P kinase; DdPPK, Dictyostelium discoideum PPK; PPX, exopolyphosphatase.
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See Commentary on page 15825.
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↵ † DdPPK1, of strain AX203a (GenBank accession no. AAD53165), has an amino acid similarity of 43% and an identity of 31% to E. coli PPK1. The null mutant (AX2M1) was used in these studies.
- Copyright © 2004, The National Academy of Sciences
