tailieunhanh - Báo cáo khoa học: The role of the ESSS protein in the assembly of a functional and stable mammalian mitochondrial complex I (NADH-ubiquinone oxidoreductase)

The ESSS protein is a recently identified subunit of mam-malian mitochondrial complex I. It is a relatively small integral membrane protein (122 amino acids) found in the b-subcomplex. Genomic sequence database searches reveal its localization to theX-chromosome inhumans andmouse. TheESSScDNAfromChinesehamster cellswas clonedand shown to complement one complementation group of our previously described mutants with a proposed X-linkage. Sequence analyses of the ESSS cDNA in these mutants revealed chain termination mutations. . | Eur. J. Biochem. 271 3265-3273 2004 FEBS 2004 doi The role of the ESSS protein in the assembly of a functional and stable mammalian mitochondrial complex I NADH-ubiquinone oxidoreductase Prasanth Potluri Nagendra Yadava and Immo E. Scheffler Division of Biology Molecular Biology Section University of California San Diego California USA The ESSS protein is a recently identified subunit of mammalian mitochondrial complex I. It is a relatively small integral membrane protein 122 amino acids found in the b-subcomplex. Genomic sequence database searches reveal its localization to the X-chromosome in humans and mouse. The ESSS cDNA from Chinese hamster cells was cloned and shown to complement one complementation group of our previously described mutants with a proposed X-linkage. Sequence analyses of the ESSS cDNA in these mutants revealed chain termination mutations. In two of these mutants the protein is truncated at the C-terminus of the targeting sequence the mutants are null mutants for the ESSS subunit. There is no detectable complex I assembly and activity in the absence of the ESSS subunit as revealed by blue native polyacrylamide gel electrophoresis BN PAGE analysis and polarography. Complex I activity can be restored with ESSS subunits tagged with either hemagglutinin HA or hexahistidine His6 epitopes at the C-terminus. Although the accumulation of ESSS-HA is not dependent upon the presence of mtDNA-encoded subunits ND1-6 4 L it is incorporated into complex I only in presence of compatible complex I subunits from the same species. Keywords complex I ESSS protein mitochondria NADH-ubiquinone oxidoreductase respiration-deficient mutants. NADH-ubiquinone oxidoreductase complex I is the first enzyme in the mitochondrial electron transport chain responsible for the oxidation of NADH. The complex I from bovine heart is composed of 46 distinct subunits of which 14 have been assigned to the core complex as homologous subunits are found