title: Binding of adenylosuccinate synthetase to contractile proteins of muscle.
abstract: The muscle isozyme of adenylosuccinate synthetase (AdSS), an enzyme of the purine nucleotide cycle, has previously been shown to bind to purified F-actin in buffers of low ionic strength and pH (Ogawa et al. Eur. J. Biochem. 85: 331-338, 1978). We have extended these observations by measuring the association of both crude and purified AdSS with the contractile proteins of muscle in buffers of physiological ionic strength and pH. Under these conditions, the enzyme binds to F-actin, actin-tropomyosin complexes, reconstructed thin filaments, and myofibrils but not to myosin. The apparent dissociation constant of 1.2 microM and binding maximum of 2.6 nmol enzyme/mg myofibrils indicate that binding of AdSS to myofibrils can be physiologically significant. The results suggest that AdSS in muscle may be associated with the thin filament of myofibrils.
authors.affiliation: Department of Medicine, Duke University, Durham, North Carolina 27710.
authors.forename: J P
authors.initials: JP
authors.lastname: Manfredi
authors.forename: R
authors.initials: R
authors.lastname: Marquetant
authors.forename: A D
authors.initials: AD
authors.lastname: Magid
authors.forename: E W
authors.initials: EW
authors.lastname: Holmes
mesh_terms: D000199:Actins / Q000378:metabolism; D000265:Adenylosuccinate Synthase / Q000378:metabolism*; D000818:Animals; D003285:Contractile Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology*; D009210:Myofibrils / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism; D009994:Osmolar Concentration; D011817:Rabbits; D014335:Tropomyosin / Q000378:metabolism
chemical_list: D000199:Actins; D003285:Contractile Proteins; D007527:Isoenzymes; D014335:Tropomyosin; D009218:Myosins; D008025:Ligases; D000265:Adenylosuccinate Synthase