Promotion of Mitochondrial Membrane Complex Assembly by a Proteolytically Inactive Yeast Lon

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Science  04 Oct 1996:
Vol. 274, Issue 5284, pp. 103-106
DOI: 10.1126/science.274.5284.103


Afg3p and Rca1p are adenosine triphosphate (ATP)-dependent metalloproteases in yeast mitochondria. Cells lacking both proteins exhibit defects in respiration-dependent growth, degradation of mitochondrially synthesized proteins, and assembly of inner-membrane complexes. Defects in growth and protein assembly, but not in degradation, were suppressed by overproduction of yeast mitochondrial Lon, an ATP-dependent serine protease. Suppression by Lon was enhanced by inactivation of the proteolytic site and was prevented by mutation of the ATP-binding site. It is suggested that the mitochondrial proteases Lon, Afg3p, and Rca1p can also serve a chaperone-like function in the assembly of mitochondrial protein complexes.