title: Amino acid sequences of two tryptic peptides from D(-)-beta-hydroxybutyrate dehydrogenase radiolabeled at essential carboxyl and sulfhydryl groups.
abstract: D(-)beta-hydroxybutyrate dehydrogenase (BDH) purified from bovine heart mitochondria contains essential thiol and carboxyl groups. A tryptic BDH peptide labeled at an essential thiol with [3H]N-ethylmaleimide (NEM), and another tryptic peptide labeled at an essential carboxyl with N,N'-dicyclohexyl [14C]carbodiimide (DCCD), were isolated and sequenced. The peptide labeled with [3H]NEM had the sequence Met.Glu.Ser.Tyr.Cys*.Thr.Ser. Gly.Ser.Thr.Asp.Thr.Ser.Pro.Val.Ile.Lys. The label was at Cys. The same peptide was isolated from tryptic digests of BDH labeled at its nucleotide-binding site with the photoaffinity labeling reagent, arylazido- -[3-3H] alanyl-NAD. These results suggest that the essential thiol of BDH is located at its nucleotide-binding site, and agree with our previous observation that NAD and NADH protect BDH against inhibition by thiol modifiers. The [14C]DCCD-labeled peptide had the sequence Glu.Val.Ala.Glu*.Val. Asn. Leu.Trp.Gly.Thr.Val.Arg. DCCD appeared to modify the glutamic acid residue marked by an asterisk. Sequence analogies between these peptides and other proteins have been discussed.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D005033:Ethylmaleimide / Q000378:metabolism; D006884:Hydroxybutyrate Dehydrogenase / Q000302:isolation & purification* / Q000378:metabolism; D008929:Mitochondria, Heart / Q000201:enzymology*; D010446:Peptide Fragments / Q000032:analysis; D011865:Radioisotope Dilution Technique; D014316:Tritium
chemical_list: D010446:Peptide Fragments; D014316:Tritium; D006884:Hydroxybutyrate Dehydrogenase; D005033:Ethylmaleimide