title: Complete amino acid sequence and in vitro expression of rat NF-M, the middle molecular weight neurofilament protein.
abstract: A lambda gtII expression library was prepared from rat brain and screened with a polyclonal antiserum, which recognizes both NF-H and NF-M. An NF-M cDNA clone (pNF-M3C = 1.6 kb) was isolated and characterized. The fusion protein of NF-M3C, when used as an affinity matrix for the anti-neurofilament serum, isolated a subpopulation of antibodies specific for NF-M. Northern analysis demonstrates a single band of approximately 3000 nt and a constant message level for NF-M during postnatal development from postnatal day 0 (PO) to adulthood. Using pNF-M3C as a probe, a second cDNA clone was isolated from a lambda gtII rat brain expression library (pNF-M2D = 2.7 kb). The 2 clones were sequenced and pNF-M2D was found to encode the entire rat NF-M protein. The calculated molecular weight is 95,600, which is only 65% of the molecular weight determined by SDS-PAGE. The amino acid sequence of rat NF-M shows the conserved rod segment present in all intermediate filament proteins. The molecule also contains an unusual C-terminal extension with stretches of glutamic acid, which could contribute to the anomalous migration of this protein on SDS-PAGE and the fact that NF-M does not readily assemble into filaments. The pNF-M2D clone was transcribed and translated in vitro utilizing a rabbit reticulocyte lysate system. The resulting radiolabeled translation products were unexpectedly shown to comigrate with purified rat NF-M on 1- and 2-dimensional gels, even though the translated protein is not phosphorylated.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001923:Brain Chemistry; D003001:Cloning, Molecular; D004247:DNA; D004587:Electrophoresis, Agar Gel; D000939:Epitopes; D007158:Immunologic Techniques; D008970:Molecular Weight; D014176:Protein Biosynthesis; D051381:Rats; D014158:Transcription, Genetic
chemical_list: D000939:Epitopes; D004247:DNA