Molecular cloning, structural characterization and chromosomal localization of human lipoyltransferase gene

Lipoyltransferase catalyzes the transfer of the lipoyl group from lipoyl-AM P to the lysine residue of the lipoate-dependent enzymes. We isolated human lipoyltransferase cDNA and genomic DNA. The cDNA insert contained a 1119-b ase pair open reading frame encoding a precursor peptide of 373 amino acids . Predicted amino acid sequence of the protein shares 88 and 31% identity w ith bovine lipoyltransferase and Escherichia coli lipoate-protein ligase A, respectively. Northern blot analyses of poly(A)(+) RNA indicated a major s pecies of about 1.5 kb. mRNA levels of lipoyltransferase were highest in sk eletal muscle and heart, showing good correlation with those of dihydrolipo amide acyltransferase subunits of pyruvate, 2-oxoglutarate and branched-cha in 2-oxo acid dehydrogenase complexes and H-protein of the glycine cleavage system which accept lipoic acid as a prosthetic group. The human lipoyltra nsferase gene is a single copy gene composed of four exons and three intron s spanning approximately 8 kb of genomic DNA. Some alternatively spliced mR NA species were found by 5'-RACE analysis, and the most abundant species la cks the third exon. The human lipoyltransferase gene was localized to chrom osome band 2q11.2 by fluorescence in situ hybridization.