Evaluation of the specific dicyclohexylcarbodiimide binding sites in brown adipose tissue mitochondria

Abstract

1. 1. The content of the membrane sector of the ATPase complex (F 0) in brown adipose tissue mitochondria was determined by means of specific [ 14C]-DCCD binding. 2. 2. The specific DCCD binding to the F 0 protein was distinguished from the nonspecific binding to the other membrane proteins and phospholipids by: (a) Scatchard plot analysis of the equilibrium binding data, (b) SDS-polyacryl-amide gel electrophoresis of the 14C-labelled membrane proteins, (c) partial purification of the chloroform-methanol extractable DCCD-binding protein. It was found that the specific DCCD binding was present in three polypeptides of a relative molecular weight of 9000, 16000 and 32000. In brown adipose tissue mitochondria the specific binding was 10-times lower than in heart or liver mitochondria. The binding to the other membrane proteins and to phospholipids was quite similar in all mitochondrial preparations studied. 3. 3. The decreased quantity of the specific binding sites in brown adipose tissue mitochondria demonstrated that the reduction of F 0 parallels the reduction of the F 1-ATPase and revealed that in these mitochondrial membranes the ratio between the respiratory chain enzymes and the ATPase complex is 10- to 20-times higher than in heart or liver mitochondria.