Cloning of the cDNA encoding a neuronal myosin heavy chain from mammalian brain and its differential expression within the central nervous system

Abstract

The complete amino acid sequence of a neuronal myosin heavy chain (MHC) from mammalian brain (1999 amino acids, 230 kDa) has been deduced by sequencing cDNA clones isolated from a rat brain cDNA library. The library was screened using an affinity-purified polyclonal antibody that had been raised against myosin purified from a neuronally-derived cell line (Neuro-2A). Restriction digests of genomic DNA from Neuro-2A cells and rat brain are consistent with an identity of the sequenced isoform from these two sources. RNA blot analysis demonstrates this myosin to exhibit differential expression within the cerebral cortex and spinal cord. No expression was observed in liver, kidney, heart, spleen or skeletal muscle, or even within other regions of the brain. The sequence of this neuronal MHC is compared with those of other non-muscle MHCs, to which it shows an overall similarity of structure, especially with respect to conserved regions within the head (ATP binding site, actin binding site, reactive thiols) and the presence of an alpha-helical coiled-coil tail that can be arranged as 28-residue repeating units plus four skip residues. A unique non-helical tailpiece composed of 72 amino acid residues marks the C-terminus of this neuronal myosin isoform.