Anti-striated muscle enriched protein kinase antibodies are used for the immunodetection of the protein encoded by the SPEG gene. In humans, the canonical protein has a reported length of 3267 amino acid residues and a mass of 354.3 kDa. Its subcellular localization is in the nucleus. Alternative splicing is reported to yield 4 different isoforms for this protein. A member of the CAMK Ser/Thr protein kinase protein family, it is known to be involved with muscle cell differentiation and muscle organ development. Post-translational modifications have been described, including phosphorylation. The gene encoding this protein is implicated in Myopathy. Other names for this target antigen include APEG1, BPEG, CNM5, MYLK6, SPEGalpha, SPEGbeta, striated muscle preferentially expressed protein kinase, and APEG-1. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.