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Inorganic polyphosphate in Dictyostelium discoideum
Author(s) -
GomezGarcia Maria Rosario,
Zhang Haiyu,
Rao Narayan N.,
Kornberg Arthur
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a900-a
Subject(s) - dictyostelium discoideum , polyphosphate , slime mold , actin , biochemistry , dictyostelium , biology , microbiology and biotechnology , biophysics , gene , phosphate
Inorganic polyphosphate (poly P) is made up of chains of tens to hundreds of phosphates, linked by the high‐energy, anhydride bonds as in ATP and found in every cell in nature. We have identified and purified many of the enzymes that make and use poly P and the genes that encode them. Prominent among them are the poly P kinases (PPKs) that makes poly P reversibly from ATP. Poly P has many functions and is essential in bacterial species for resistance to variety of stresses (heat, drying, oxidants, predation), and for the virulence of pathogens. Dictyostelium discoideum (Dd), the social slime mold, has two polyphosphate kinases: DdPPK1 with homology to bacterial PPK; Knockouts of DdPPK1 are defective in predation and sporulation. DdPPK2 is a novel actin‐like complex of three actin‐related‐proteins (Arp1, Arp2 and Act28). These resemble muscle actins in size, globular‐filamentous (G‐F) transitions and inhibition by phalloidin and DNase I. Thus, this enzyme assembles itself into a filament from globular complexes concurrent with its synthesis of a poly P chain. The reaction is fully reversible. Single knockouts of Arp1 and Act 28 show decreased levels of poly P, PPK2 activity and defects in development; the Arp2 knockout is not viable. Inclusion, singly, of Arp1, 2 and 28 in a baculovirus vector and subsequent PPK2 expression in insect cells requires co‐infection of all three baculovirus vectors. Thus, the synthesis of poly P by DdPPK2 conserves the energy wasted in the hydrolytic ATPase commonly associated with actin G‐F transitions. Funds for support of this research were supplied by NIH.