Murphy A M, Jones L, Sims H F, Strauss A W
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110.
Biochemistry. 1991 Jan 22;30(3):707-12. doi: 10.1021/bi00217a018.
We have isolated and sequenced a cDNA encoding rat cardiac troponin I. The predicted amino acid sequence was highly identical with previously reported chemically derived amino acid sequences for rabbit and bovine cardiac troponin I. Clones for slow skeletal muscle troponin I were also obtained from neonatal rat cardiac ventricle by the polymerase chain reaction. The nucleotide sequences of these clones were determined to be more than 99% identical with a previously reported rat slow skeletal troponin I cDNA [Koppe et al. (1989) J. Biol. Chem. 264, 14327-14333]. The troponin I clones hybridized to RNA from the appropriate muscle from adult animals. However, RNA from fetal and neonatal rat heart also hybridized with the slow skeletal troponin I cDNA, demonstrating its expression in fetal and neonatal rat heart. Slow skeletal troponin I steady-state mRNA levels decreased with increasing age, but cardiac troponin I mRNA levels increased through fetal and early neonatal cardiac development. Thus, during fetal and neonatal development, slow skeletal and cardiac troponin I isoforms are coexpressed in the rat heart and regulated in opposite directions. The degree of primary sequence differences in these isoforms, especially at phosphorylation sites, may result in important functional differences in the neonatal myocardium.
我们已经分离并测序了编码大鼠心肌肌钙蛋白I的cDNA。预测的氨基酸序列与先前报道的兔和牛心肌肌钙蛋白I的化学衍生氨基酸序列高度相同。通过聚合酶链反应也从新生大鼠心室中获得了慢骨骼肌肌钙蛋白I的克隆。这些克隆的核苷酸序列被确定与先前报道的大鼠慢骨骼肌肌钙蛋白I cDNA[科佩等人（1989年）《生物化学杂志》264卷，14327 - 14333页]有超过99%的同一性。肌钙蛋白I克隆与成年动物相应肌肉的RNA杂交。然而，来自胎儿和新生大鼠心脏的RNA也与慢骨骼肌肌钙蛋白I cDNA杂交，表明其在胎儿和新生大鼠心脏中的表达。慢骨骼肌肌钙蛋白I的稳态mRNA水平随着年龄增长而降低，但心肌肌钙蛋白I的mRNA水平在胎儿和新生儿早期心脏发育过程中升高。因此，在胎儿和新生儿发育过程中，慢骨骼肌和心肌肌钙蛋白I同工型在大鼠心脏中共同表达且呈相反方向调节。这些同工型一级序列差异的程度，尤其是在磷酸化位点，可能导致新生儿心肌中重要的功能差异。
