Carnitine palmitoyltransferase II deficiency: structure of the gene and characterization of two novel disease-causing mutations

摘要: Carnitine palmitoyltransferase (CPT) II deficiency is the most common inherited disorder of lipid metabolism affecting skeletal muscle. To facilitate identification disease-causing mutations in CPT gene (CPT1), we have established genomic organization this gene. CPT1 spans approximately 20 kb 1p32 and composed five exons ranging from 81 to 1305 bp. The sequences exon--intron boundaries were determined for each exon conformed consensus splice junction sequences. 5' 3' untranslated regions 1 5, respectively, also determined, including polyadenylation signal site. mature transcript predicted be 3090 nt length. II-deficient patients amplified directly sequenced. Two novel identified characterized. first mutation was a C-665-to-A transversion resulting proline-to-histidine substitution at residue 50 protein (P50H). This amino acid occurs within leucine-proline motif that highly conserved acyltransferases different species. detected both alleles patient 05SB Italian ancestry, one allele 11EG, 38PG, 26FD Italian, Dutch, French respectively. second rare G-2173-to-A transition 5 causing an aspartic-acid-to-asparagine 553 (D553N) generation new MseI only 15MB, who heterozygous S113L substitution. Transfection experiments COS cells demonstrated drastically depressed catalytic activity II. Biochemical characterization P50H mutant cultured showed does not affect substrate binding sites. Finally, immunoblot analysis associated with markedly reduced steady-state level protein, thus indicating decreased stability