ASSEMBLY OF MITOCHONDRIAL ATP SYNTHASE IN CULTURED HUMAN-CELLS - IMPLICATIONS FOR MITOCHONDRIAL DISEASES

To study the assembly of mitochondrial F1F0 ATP synthase, cultured hum an cells were labeled with [S-35]methionine in pulse-chase experiments . Next, two-dimensional electrophoresis and fluorography were used to analyze the assembly pattern. Two assembly intermediates could be demo nstrated. First the F-1 part appeared to be assembled, and next an int ermediate product that contained F-1 and subunit c. This product proba bly also contained subunits b, F6 and OSCP, but not the mitochondriall y encoded subunits a and A6L. Both intermediate complexes accumulated when mitochondrial protein synthesis was inhibited, suggesting that mi tochondrially encoded subunits are indispensable for the formation of a fully assembled ATP synthase complex, but not for the formation of t he intermediate complexes. The results and methods described in this s tudy offer an approach to study the effects of mutations in subunits o f mitochondrial ATP synthase on the assembly of this complex. This mig ht be of value fora better understanding of deficiencies of ATP syntha se activity in mitochondrial diseases.