Functional consequences of the deletion mutation deltaGlu160 in human cardiac troponin T.
To explore the functional consequences of a deletion mutation of troponin T (DeltaGlu160) found in familial hypertrophic cardiomyopathy, the mutant human cardiac troponin T, and wild-type troponins T, I, and C were expressed in Escherichia coli and directly incorporated into isolated porcine cardiac myofibrils using our previously reported troponin exchange technique. The mutant troponin T showed a slightly reduced potency in replacing the endogenous troponin complex in myofibrils and did not affect the inhibitory action of troponin I but potentiated the neutralizing action of troponin C, suggesting that the deletion of a single amino acid, Glu-160, in the strong tropomyosin-binding region affects the tropomyosin binding affinity of the entire troponin T molecule and alters the interaction between troponin I and troponin C within ternary troponin complex in the thin filament. This mutation also increased the Ca(2+) sensitivity of the myofibrillar ATPase activity, as in the case of other mutations in troponin T with clinical phenotypes of poor prognosis similar to that of Glu160. These results provide strong evidence that the increased Ca(2+) sensitivity of cardiac myofilament is a typical functional consequence of the troponin T mutation associated with a malignant form of hypertrophic cardiomyopathy.
Harada
K
K
Department of Clinical Pharmacology, Graduate School of Medical Sciences, Kyushu University, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Takahashi-Yanaga
F
F
Minakami
R
R
Morimoto
S
S
Ohtsuki
I
I
D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000187:drug effects / Q000378:metabolism; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics; D006801:Humans; D009206:Myocardium / Q000737:chemistry; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017384:Sequence Deletion; D013552:Swine; D014335:Tropomyosin / Q000378:metabolism; D019209:Troponin C / Q000235:genetics / Q000494:pharmacology; D019210:Troponin I / Q000235:genetics / Q000494:pharmacology; D020107:Troponin T / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology
D011994:Recombinant Proteins; D014335:Tropomyosin; D019209:Troponin C; D019210:Troponin I; D020107:Troponin T; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D002118:Calcium