Early specialization of the superfast myosin in extraocular and laryngeal muscles.

摘要: Extraocular muscle (EOM) exhibits high-velocity, low-tension contractions compared with other vertebrate striated muscles. These distinctive properties have been associated a novel myosin heavy chain (MyHC) isoform, MyHC-EO. An atypical MyHC, MyHC IIL, has also identified in laryngeal muscles that similarly fast contractile properties. It co-migrates MyHC-EO on high-resolution SDS gels, but appeared to be encoded by different mRNA. We combined CNBr peptide maps and full-length cDNA sequences show rabbit EO IIL MyHCs are identical. Analysis of the 5; untranslated region (5;UTR) mRNAs three variants result from combination alternative splicing multiple transcription initiation sites. This complex pattern 5;UTRs not reported previously for genes. human homologue gene GenBank, analyzed upstream region, which revealed paucity muscle-specific factor binding sites features likely critical unique regulation tissue-specific expression MyHC-EO/IIL gene.Phylogenetic analysis indicates diverged an ancestral generate first specialized myosin. The catalytic S1 head domain is more closely related MyHCs, while rod slow/cardiac MyHCs. exon boundaries identical those embryonic virtually α (β) cardiac implies most current were present gene, predating duplications generated family skeletal