Effect of Arg145Gly mutation in human cardiac troponin I on the ATPase activity of cardiac myofibrils.
In order to determine the functional consequences of the Arg145Gly mutation in troponin I found in familial hypertrophic cardiomyopathy, human cardiac troponin I and its mutant were expressed in Escherichia coli and purified, and then their effects on the ATPase activity of porcine cardiac myofibrillar preparations from which both troponins C and I had been depleted were examined. Both the wild-type and mutant troponin Is suppressed the ATPase activity of the troponin C.I-depleted myofibrils, but the maximum inhibition caused by mutant troponin I was weaker than that by wild-type troponin I. In the Ca(2)(+)-activation profile of the myofibrillar ATPase activity after reconstitution with both troponins I and C, the Ca(2)(+)-sensitivity with mutant troponin I was higher than that with wild-type troponin I, whereas the maximum level of the ATPase activity with mutant troponin I was lower than that with wild-type troponin I. These findings strongly suggest that the Arg145Gly mutation in human cardiac troponin I modulates the Ca(2)(+)-regulation of contraction by impairing the interaction of troponin I with both actin-tropomyosin and troponin C.
Takahashi-Yanaga
F
F
Laboratory of Clinical Pharmacology, Department of Pharmacological Sciences, Graduate School of Medicine, Kyushu University, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. yanaga@clipharm.med.kyushu-u.ac. jp
Morimoto
S
S
Ohtsuki
I
I
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000737:chemistry; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics; D018076:DNA, Complementary; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D005998:Glycine / Q000737:chemistry; D006801:Humans; D016296:Mutagenesis; D009154:Mutation; D009206:Myocardium / Q000648:ultrastructure*; D009210:Myofibrils / Q000201:enzymology*; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry; D019210:Troponin I / Q000737:chemistry* / Q000235:genetics*
D018076:DNA, Complementary; D011994:Recombinant Proteins; D019210:Troponin I; D001120:Arginine; D000251:Adenosine Triphosphatases; D005998:Glycine