cDNA cloning and chromosomal mapping of mouse fast skeletal muscle troponin T

• Published in: Mammalian genome 1997-05, Vol.8 (5), p.346-348
• Main Authors: Koch, A, Juan, T S, Jenkins, N A, Gilbert, D J, Copeland, N G, McNiece, I K, Fletcher, F A
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Calcium-binding protein; Chromosome Mapping; Cloning; Cloning, Molecular; Conserved Sequence; DNA, Complementary - genetics; Female; Gene mapping; Male; Mice; Mice, Inbred C57BL; Molecular Sequence Data; Muridae; Muscle Fibers, Fast-Twitch - metabolism; Muscle, Skeletal - metabolism; Rats; Sequence Homology, Nucleic Acid; Skeletal muscle; Space life sciences; Species Specificity; Troponin; Troponin - genetics; Troponin T
• ISSN: 0938-8990; 1432-1777
• DOI: 10.1007/s003359900437

Calcium-dependent contraction of vertebrate striated muscle is regulated in part through the interaction of the troponin protein complex with tropomyosin and the actin-myosin myofibril. The troponin complex consists of three proteins, troponin I (TnI), troponin C (TnC), and troponin T (TnT). TnI is an actin-binding protein that enables the troponin complex to physically inhibit the interaction of myosin and actin, thus preventing muscle contraction in the absence of excitation-induced elevated intracellular Ca super(2+). TnC is a calcium-binding protein that can, in the presence of elevated intracellular Ca super(2+), reverse the TnI-induced inhibition of actin-myosin binding, thus initiating muscle contraction. TnT is a tropomyosin-binding protein that is thought to position the troponin complex on the myofibril. The troponin proteins are encoded by three distinct gene families. The two TnC genes encode distinct protein isoforms found either in fast skeletal muscle or slow skeletal and cardiac muscle. The TnI and TnT gene families each consist of three separate genes encoding protein isoforms found in cardiac, slow skeletal, or fast skeletal muscle, respectively. The murine TnC and TnI genes have all been cloned and, with the exception of fast skeletal muscle troponin C, chromosomally mapped, while none of the TnT genes have been mapped in the mouse genome. Fast skeletal muscle troponin T cDNAs encoding various protein isoforms have been described from several vertebrate sources, including rat and human, but a full-length cDNA sequence or chromosomal localization of the mouse gene has not been reported. We recently cloned an adult mouse fast skeletal muscle troponin T cDNA. The 996-bp cDNA encoded an 815-bp open reading frame that was 96.5% identical to the orthologous rat cDNA. There was no in-frame stop codon upstream of the predicted translational start methionine (similar to the rat cDNA), but the 5' and 3' ends of the mouse and rat clones coincided. The 3'-untranslated region of the mouse cDNA contained a poly(A) addition signal (aataaa, nt 977-982) at precisely the same position at that found in the rat cDNA. Since the cDNAs from mouse and rat are so highly conserved, and since the 5' and 3' ends of cDNAs from the two species coincided, we suggest that a full-length splice variant of mouse fast troponin T was cloned.