Molecular cloning of rat cardiac sarcolemmal Ca2+/Mg2+ ectoATPase (Myoglein)

Rat cardiac sarcolemmal Ca2+/Mg2+ ectoATPase (Myoglein), a membrane-bound e nzyme requiring millimolar concentrations of Ca2+ or Mg2+ for maximal hydro lysis of ATP, has been purified to apparent homogeneity. Tryptic digestion and amino acid sequencing was used to design an oligonucleotide probe for s creening a rat heart cDNA library; this produced a partial cDNA. clone (pND 2.1), and sequencing of a 400 base pair portion revealed a 100% homology to human platelet CD36. Northern blotting with pND2.1 detected a 3.1 kb trans cript in rat heart but not in other tissues. Interspecies expression analys is (cardiac tissue total RNA blot probed with pND2.1) detected a similar to 2.0 kb transcript in canine, rabbit and porcine heart, whereas transcripts of a 4.1 kb, similar to 3.0 kb and 2.1 kb were observed in human cardiac t issue. A rat genomic DNA Southern blot, probed with pND2.1, indicated that there was a single copy of the gene in the rat genome. Expression of the pN D2.1 cDNA in E. coli produced an 89 kDa polypeptide recognized by anti-huma n CD36 antibody but not by anti-rat Ca2+/Mg2+ ectoATPase antibody. It is co ncluded that fat cardiac Ca2+/Mg2+ ectoATPase is tightly associated with a protein highly homologous to the adhesion molecule CD36. (C) 1998 Academic Press.