Diffusion hindrance and geometry of filament crossings account for the complex interactions of F-actin with alpha-actinin from chicken gizzard.
The interaction of alpha-actinin from chicken gizzard with F-actin is quite complex. The apparent dissociation constant, C, increases with the increase of actin concentration according to the following expression: C = Ko + a[actin] - c[actin]5/2. At pH 7.5 and 37 degrees C, in the presence of 0.1 M KCl and 2 mM MgCl2, the dissociation constant at infinite actin dilution, Ko, is 2.17 microM. The binding of alpha-actinin to actin is related by the term a[actin] to the diffusion of actin filaments and by the term c[actin]5/2 to the crossing number concentration of the F-actin network. Especially at low actin concentration, the binding of alpha-actinin to actin is increased by gelsolin, which fragments actin filaments and increases their diffusion. The different binding isotherms of alpha-actinin to actin filaments and to actin bundles are discussed.
Istituto di Chimica Biologica, Università di Ferrara, Italy.
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Magri
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Schwienbacher
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Trombetta
D000185:Actinin / Q000737:chemistry / Q000378:metabolism*; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D002645:Chickens; D004058:Diffusion; D018260:Gelsolin; D005895:Gizzard, Avian / Q000378:metabolism*; D008840:Microfilament Proteins / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011817:Rabbits
D000199:Actins; D002135:Calcium-Binding Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; D000185:Actinin