Functional and Structural Basis of Carnitine Palmitoyltransferase 1A Deficiency

Abstract

Carnitine palmitoyltransferase 1A (CPT1A) is the key regulatory enzyme of hepatic long-chain fatty acid ␤-oxidation. Human CPT1A deficiency is characterized by recurrent attacks of hypoketotic hypoglycemia. We presently analyzed at both the functional and structural levels five missense mutations identified in three CPT1A-deficient patients, namely A275T, A414V, Y498C, G709E, and G710E. Heterologous expression in Saccharomyces cerevisiae permitted to validate them as disease-causing mutations. To gain further insights into their deleterious effects, we localized these mutated residues into a three-dimensional structure model of the human CPT1A created from the crystal structure of the mouse carnitine acetyltransferase. This study demonstrated for the first time that disease-causing CPT1A mutations can be divided into two categories depending on whether they affect directly (functional determinant) or indirectly the active site of the enzyme (structural determinant). Mutations A275T, A414V, and Y498C, which exhibit decreased catalytic efficiency, clearly belong to the second class. They are located more than 20 Å away from the active site and mostly affect the stability of the protein itself and/or of the enzyme-substrate complex. By contrast, mutations G709E and G710E, which abolish CPT1A activity, belong to the first category. They affect Gly residues that are essential not only for the structure of the hydrophobic core in the catalytic site, but also for the chain-length specificity of CPT isoforms. This study provides novel insights into the functionality of CPT1A that may contribute to the design of drugs for the treatment of lipid disorders.

Third Annual World Congress on the Insulin Resistance Syndrome

“…New discoveries are the association of the PTPN22 phosphatase allele with rheumatoid arthritis (76) and a number of other autoimmune diseases, and of the association of two gene variants, the DDX5 Ser480Ala polymorphism of a RNA helicase (ATPase) involved in RNA unwinding and RNA binding (77), and the carnitine palmitoyltransferase 1a Ala275Thr polymorphism (78), with advanced hepatic fibrosis in hepatitis C, suggesting that it may be possible to characterize persons with NAFLD who are at 10-fold higher risk of progression and hence in need of treatment. These genes may lead to drug discovery and may allow optimal risk stratification for clinical trials.…”

Conformational Analysis of Invariant Peptide Sequences in Bacterial Genomes

“…These conserved regions are sometimes referred to as the structural determinants (SD) of the proteins. 3 It has also been demonstrated that the residues involved in the folding nuclei of the proteins are evolutionarily conserved. 4 However, significant controversy exists in this regard in the literature.…”

Microarray analysis of perichondral and reserve growth plate zones identifies differential gene expressions and signal pathways

“…Reticulocalbin (Rcn1), which is distributed predominantly in endocrine and exocrine organs, is one member of the Ca 2+ -binding proteins in the secretory pathway [24]. Carnitinine palmitoyltransferase 1A (Cpt1a) is the key regulatory enzyme of hepatic long-chain fatty acid β-oxidation [25]. Cpt1A is also known to regulate apoptotic processes [26].…”