tailieunhanh - Báo cáo khoa học: Assembly of nuclear DNA-encoded subunits into mitochondrial complex IV, and their preferential integration into supercomplex forms in patient mitochondria

Complex IV is the terminal enzyme of the mitochondrial respiratory chain. In humans, biogenesis of complex IV involves the coordinated assembly of 13 subunits encoded by both mitochondrial and nuclear genomes. The early stages of complex IV assembly involving mitochondrial DNA-encoded subunits CO1 and CO2 have been well studied. | Assembly of nuclear DNA-encoded subunits into mitochondrial complex IV and their preferential integration into supercomplex forms in patient mitochondria Michael Lazarou1 Stacey M. Smith1 2 David R. Thorburn2 Michael T. Ryan1 and Matthew McKenzie1 1 Department of Biochemistry La Trobe University Melbourne Australia 2 Murdoch Children s Research Institute and Genetic Health Services Victoria RoyalChildren s Hospital and Department of Pediatrics University of Melbourne Australia Keywords complex IV cytochrome c oxidase membrane proteins mitochondria oxidative phosphorylation Correspondence M. T. Ryan Department of Biochemistry La Trobe University 3086 Melbourne Australia Fax 61 3 94792467 Tel 61 3 94792156 E-mail Received 4 June 2009 revised 18 August 2009 accepted 16 September 2009 doi Complex IV is the terminal enzyme of the mitochondrial respiratory chain. In humans biogenesis of complex IV involves the coordinated assembly of 13 subunits encoded by both mitochondrial and nuclear genomes. The early stages of complex IV assembly involving mitochondrial DNA-encoded subunits CO1 and CO2 have been well studied. However the latter stages during which many of the nuclear DNA-encoded subunits are incorporated are less well understood. Using in vitro import and assembly assays we found that subunits Cox6a Cox6b and Cox7a assembled into pre-existing complex IV while Cox4-1 and Cox6c subunits assembled into subcomplexes that may represent rate-limiting intermediates. We also found that Cox6a and Cox7a are incorporated into a novel intermediate complex of approximately 250 kDa and that transition of subunits from this complex to the mature holoenzyme had stalled in the mitochondria of patients with isolated complex IV deficiency. A number of complex IV subunits were also found to integrate into supercomplexes containing combinations of complex I dimeric complex III and complex IV. Subunit assembly into these .