Comparison of solubility properties of α-paramyosin, β-paramyosin, and acid-extracted paramyosin

Abstract

The solubility properties of paramyosin [from Mercenaria mercenaria adductor muscle] in the zones of pH and ionic strength in which aggregation occurs were initially studied using preparations isolated by a method originally described by Bailey (1956). Other preparations yielding apparently different protein components were described by Hodge (1952) using acid conditions, and Stafford and Yphantis (1972) identified .alpha.-, .beta.-, and .gamma.-paramyosin using various times and temperatures of extraction with or without EDTA. Acid-extracted paramyosin was very similar if not identical to .alpha.-paramyosin, but both acid and .alpha. forms differed considerably from .beta.- and .gamma.-paramyosin. .beta.-Paramyosin precipitated abruptly from solution in a narrow zone of pH below neutrality and increases in ionic strength shifted the zone of precipitation toward lower pH values. Acid and .alpha.-paramyosin showed gradual aggregation with changing pH at lower ionic strength (< 0.3) but sharp transitions similar to .beta.-paramyosin at higher ionic strength (> 0.3). Transitions were found at lower pH (.apprx. 4.0) which were not mirror images of transitions at higher pH (.apprx. 7.0). Viscosity measurements showed that acid extracted paramyosin was close in behavior to a native extract obtained by extraction in mild, nondenaturing media containing mixed antibiotics. Each differed considerably from .beta.-paramyosin. Mild, nonhydrolytic procedures employed by others to remove small, noncovalent bonded components or to separate protein complexes were not effective in converting .alpha.- to .beta.-paramyosin. Comparison of extraction procedures supported the suggestion of Stafford and Yphantis that .beta.- and .gamma.-paramyosin are hydrolytic products of .alpha.-paramyosin and that proteases responsible may be of bacterial origin.