The phosphorylation of subunits of complex I from bovine heart mitochondria.
In bovine heart mitochondria and in submitochondrial particles, membrane-associated proteins with apparent molecular masses of 18 and 10 kDa become strongly radiolabeled by [(32)P]ATP in a cAMP-dependent manner. The 18-kDa phosphorylated protein is subunit ESSS from complex I and not as previously reported the 18 k subunit (with the N-terminal sequence AQDQ). The phosphorylated residue in subunit ESSS is serine 20. In the 10 kDa band, the complex I subunit MWFE was phosphorylated on serine 55. In the presence of protein kinase A and cAMP, the same subunits of purified complex I were phosphorylated by [(32)P]ATP at the same sites. Subunits ESSS and MWFE both contribute to the membrane arm of complex I. Each has a single hydrophobic region probably folded into a membrane spanning alpha-helix. It is likely that the phosphorylation site of subunit ESSS lies in the mitochondrial matrix and that the site in subunit MWFE is in the intermembrane space. Subunit ESSS has no known role, but subunit MWFE is required for assembly into complex I of seven hydrophobic subunits encoded in the mitochondrial genome. The possible effects of phosphorylation of these subunits on the activity and/or the assembly of complex I remain to be explored.
Chen
Ruming
R
Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK.
Fearnley
Ian M
IM
Peak-Chew
Sew Y
SY
Walker
John E
JE
D000255:Adenosine Triphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism; D042967:Electron Transport Complex I; D004591:Electrophoresis, Polyacrylamide Gel; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000737:chemistry*; D008928:Mitochondria / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism*; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014357:Trypsin / Q000737:chemistry
D004272:DNA, Mitochondrial; D008565:Membrane Proteins; C492251:Ndufa1 protein, mammalian; D010455:Peptides; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D014357:Trypsin; D042967:Electron Transport Complex I