Binding of aldolase to actin-containing filaments. Quantitative reappraisal of the interactions.
Previously reported results of equilibrium-partition experiments on the interaction of aldolase with actin-containing filaments [Walsh, Winzor, Clarke, Masters & Morton (1980) Biochem. J. 186, 89-98] have been subjected to a more rigorous theoretical analysis involving consideration of the consequences of cross-linking interactions between enzyme and filament. The experimental results obtained with F-actin-tropomyosin are best described by a model with one binding site per heptameric repeat unit of filament and a value of 39000 M-1 for the site binding constant, k. Similar analyses of the influence of Ca2+ on aldolase binding to F-actin--tropomyosin--troponin substantiate the existence of two equivalent binding sites (k = 14900 M-1) for the enzyme on each repeat unit of the thin filament. The Ca2+-sensitivity of this interaction reflects either a decrease in the strength of aldolase binding to these two sites (k = 8200 M-1) or the elimination of one site.
D000199:Actins; D001665:Binding Sites; D002118:Calcium; D005634:Fructose-Bisphosphate Aldolase; D008954:Models, Biological; D009210:Myofibrils / Q000378:metabolism*; D011485:Protein Binding; D014335:Tropomyosin
D000199:Actins; D014335:Tropomyosin; D005634:Fructose-Bisphosphate Aldolase; D002118:Calcium