The Effects of Neutral Salts and Nucleotides on the Stability of Beef Heart Mitochondrial F₁-ATPase

Abstract

Analysis of upwards of 30 preparations of beef heart mitochondrial F₁-ATPase by size exclusion HPLC revealed that these highly purified enzyme preparations contain, on the average, 10 to 15% dissociated enzyme, or inactive polymers. In a few preparations, most notably several chloroform extracts (Spitsberg and Blair, 1977), as much as 50% of the total protein consists of subunits and high molecular weight aggregates. Despite the well known propensity of the major beef heart F₁ subunits^a to form a white insoluble precipitate (e.g. Knowles and Penefsky, 1972), crystal clear solutions containing upwards of 2 mg/ml disaggregated subunits, as well as native F₁, may be obtained at room temperature. The cold lability of the enzyme is well known, and it might be surmised that dissociation occurs during long term storage at reduced temperatures. However no obvious correlation was found between the age of a particular F₁ preparation and the extent of dissociation.