N-terminal sequence of creatine kinase from skeletal muscle of rabbit and rhesus monkey

The first 20 amino acids from the N-terminus of skeletal muscle (MM) creatine kinase from both rabbit and rhesus monkey have been identified and these sequences show considerable homology. Contrary to an earlier report, the N-terminus was not found to be blocked. Both of these sequences show much less homology with the N-terminal sequence of heart muscle (MM) creatine kinase and no homology with that of the heart muscle mitochondrial (MiMi) isozyme. No homology was found between the N-terminal sequence of the mitochondrial isozyme and the URF (unidentified reading frame) proteins of the human mitochondrial genome, indicating that the mitochondrial enzyme is encoded by nuclear genes. This suggests the possibility that an N-terminal peptide may be cleaved from the mitochondrial isozyme on its translocation across the mitochondrial membrane.