Complete nucleotide sequence of Torpedo marmorata mRNA coding for the 43,000-dalton nu 2 protein: muscle-specific creatine kinase.

DNA sequences coding for the muscle-specific subunit of creatine kinase have been isolated from cDNA libraries constructed from Torpedo marmorata electric organ. Clones were screened by differential in situ hybridization and hybrid-selected translation. The in vitro translation product of the selected mRNA was immunoprecipitated by anti-chicken creatine kinase antibodies and comigrated with Torpedo muscle creatine kinase on two-dimensional gels at the same position as the cytosolic 43,000-dalton protein referred to as nu 2. The cDNA inserts hybridized to a mRNA species present in adult Torpedo muscle but not in brain. The complete sequence of the mRNA was determined on one of the clones except for the 78 nucleotides of the mRNA 5' terminal sequence, which were identified by the primer extension method. The amino acid sequence of muscle-specific creatine kinase from T. marmorata was deduced and analyzed. It includes the known sequence of a peptide from the active site of rabbit muscle-specific creatine kinase.