title: Sequence of the N-terminal formic acid fragment and location of the N-ethylmaleimide-binding site of the phosphate transport protein from beef heart mitochondria.
abstract: The N-terminal formic acid fragment (FA1) of the N-[3H]ethylmaleimide-labeled and carboxymethylated bovine mitochondrial phosphate transport protein (PTPN*CM) has been purified and completely sequenced: NH2-Ala-Val-Glu-Glu-Gln-Tyr-Ser-Cys-Asp-Tyr10-Gly-Ser-Gly-Arg-Phe- Phe-Ile-Leu-Cys- Gly20-Leu-Gly-Gly-Ile-Ile-Ser-Cys-Gly-Thr-Thr30-His-Thr -Ala-Leu-Val-Pro-Leu-Asp- -Leu-Val40-Lys-Cys(N-[3H]ethylmaleimide)-Arg-Met-Gln-Val-Asp- COOH. By thermolysin digestion of FA1 and high-performance liquid chromatography isolation of the radioactive subfragment Leu39-Arg43, the sole N-ethylmaleimide-binding residue has been identified as Cys42. FA1 contains a high mole percentage of cysteine (8.5%) and shows silver staining anomaly. Its sequence reveals significant homology in the triplicated gene regions (Pro27,132,229) of the mitochondrial ADP/ATP carrier from beef heart and Neurospora crassa. The hydropathic profile suggests that FA1 contains a transmembrane segment (Phe15-Val40) with only one basic (His31) and one acidic (Asp38) residue. The presence of the phosphate transport protein gene among nuclear genes is suggested from a lack of significant homology between the reverse-translated FA1 (mitochondrial codons) and the bovine mitochondrial genome. The inhibitory action of N-ethylmaleimide on the phosphate transport mechanism is discussed.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D003488:Cyanogen Bromide / Q000494:pharmacology; D003545:Cysteine / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D005033:Ethylmaleimide / Q000378:metabolism*; D005470:Fluorometry; D005561:Formates / Q000494:pharmacology*; D008929:Mitochondria, Heart / Q000032:analysis*; D000226:Mitochondrial ADP, ATP Translocases / Q000032:analysis; D010446:Peptide Fragments / Q000032:analysis*; D028044:Phosphate-Binding Proteins; D012834:Silver
chemical_list: D002352:Carrier Proteins; D005561:Formates; D010446:Peptide Fragments; D028044:Phosphate-Binding Proteins; C030544:formic acid; D012834:Silver; D000226:Mitochondrial ADP, ATP Translocases; D003545:Cysteine; D005033:Ethylmaleimide; D003488:Cyanogen Bromide