A Unique Cellular Myosin II Exhibiting Differential Expression in the Cerebral Cortex

Clones possessing inserts of brain myosin II have been obtained by screening a rat brain cDNA expression library with a polyclonal antibody, raised against myosin II from the mouse neuroblastoma cell line, Neuro-2A. A partial sequence comprising the 3' coding and non-coding regions of the myosin message has been determined which is markedly different from other myosin sequences. The derived amino-acid sequence comprises the C-terminal 90 amino acids: VSS(PO4)LKNKLRRGDLPFVVTRRLVRKGTLELS(PO4)DDDDESKASLINETQPPQCLDQQ LDQQ LDQLFNWPVNAGCVCGWGVEQTQGEEAVHKCRT(CO2H). This sequence encompasses regions homologous to both the casein kinase II and protein kinase C heavy-chain phosphorylation sites. The non-helical "tail-piece" is considerably longer (an additional 39 amino acid residues) than found in other myosins. Northern blot analysis demonstrates this myosin II message to be unique to cerebral cortex, with no expression in all other non-cortical brain regions and peripheral tissues tested. Our results suggest functional diversity for myosin II isozymes within the brain.