P1.64 Jan. 4 Characterization of a novel isoform of lobster troponin C and expression in skeletal muscles. CHAO, E.*; KIM, H.W.; THOMPSON, M.D.; MYKLES, D.L.; Colorado State University; Colorado State University; Colorado State University; Colorado State University email@example.com
Troponin C (TnC) is a muscle protein that mediates calcium-dependent regulation of muscle contraction. In the lobster, three TnC protein isoforms (designated TnC-1, TnC-2a, & TnC-2b) have been previously identified and their amino acid (aa) sequences published. We cloned a full-length cDNA encoding a novel fourth isoform of TnC, designated TnC-3 (1.2 kb, 150 amino acids, ~16.8 kDa). The current study aims to clone cDNAs encoding the other three isoforms using RT-PCR. Four partial TnC cDNA sequences (Cr, Cu, DA1 and DA3) were cloned from the crusher (Cr), cutter (Cu), and deep abdominal (DA) muscles, respectively. All were 249 bp in length and encoded a 97-aa sequence. The sequences shared 81-98 % aa sequence identities. The deduced aa sequences of the Cu and DA1 cDNAs were identical to the aa sequences of TnC gamma from the narrow-clawed crayfish, Pontastacus leptodactylus (accession number B34380) and TnC-1 (accession number AAA03250), respectively. These data suggest that there are at least seven TnC isoforms in lobster muscles. Further work will determine: expression patterns of TnC isoforms in each muscle fiber type; how this relates to muscle functional properties; whether TnC can be used as an indicator of fiber type switching; and whether fiber type switching and changes in TnC isoforms change in response to muscular changes that occur over the molt in response to levels of myostatin, a hormone which inhibits muscle growth. Supported by NSF (IBN-0618203).