This basic science study maps the topology of the troponin complex, revealing that troponin-I and -T are within 0.6 nm of each other and that cross-linking abolishes calcium sensitivity of actomyosin ATPase.
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Remains preclinical; extends troponin structural models while leaving open in vivo roles in contractile dysfunction.
The topology of troponin, the calcium binding regulatory protein in muscle, has been studied by cross-linking with different length dimethylimido esters. The results show that the three components of troponin are close to each other and that the troponin-I and -T are preferentially cross-linked being 0.6 nm or less apart. The largest cross-linked product is a complex which corresponds in molecular weight to the native troponin complex of 1 mol of each of the three components. Cross-linked troponin has lost the ability to make the actomyosin ATPase calcium sensitive although it does bind to actin-tropomyosin and tropomyosin, and it binds calcium normally. No effect of calcium on cross-linking could be detected.
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Sarah E. Hitchcock (1975) studied this question.
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