Sutoh K, Matsuzaki F
Biochemistry. 1980 Aug 5;19(16):3878-82. doi: 10.1021/bi00557a037.
Troponin I (TnI) was reacted with a photosensitive heterobifunctional reagent, methyl 4-azidobenzimidate (ABI), and then troponin was reconstituted with the ABI-modified TnI. Flash irradiation of the reconstituted troponin resulted in the formation of cross-links between TnI and other components of troponin, troponin C (TnC) and troponin T (TnT), suggesting that TnI is in contact with TnC and TnT when troponin is free in solution. No effect of calcium on the cross-linking could be detected. When the reconstituted troponin was complexed with F-actin-tropomyosin, flash irradiation of the reconstituted then filament yielded the cross-linked products of TnC-TnI, TnI-TnT, and TnI-actin in the presence ans absence of calcium, indicating that TnI is in contact with TnC, TnT, and actin in the thin filament complex irrespective of calcium concentration. No cross-linking could be detected between TnI and tropomyosin. Calcium was found to affect the cross-linking of TnC-TnI and TnI-actin; when TnC was saturated with calcium, the extent of the TnC-TnI cross-linking increased, while that of the TnI-actin cross-linking decreased. Calcium did not affect the TnI-TnT cross-linking.
肌钙蛋白I（TnI）与一种光敏异双功能试剂4-叠氮基苯甲酸甲酯（ABI）反应，然后用ABI修饰的TnI重构肌钙蛋白。对重构后的肌钙蛋白进行闪光照射，导致TnI与肌钙蛋白的其他成分，即肌钙蛋白C（TnC）和肌钙蛋白T（TnT）之间形成交联，这表明当肌钙蛋白在溶液中游离时，TnI与TnC和TnT接触。未检测到钙对交联的影响。当重构后的肌钙蛋白与F-肌动蛋白-原肌球蛋白复合时，对重构后的细丝进行闪光照射，无论有无钙存在，均产生TnC-TnI、TnI-TnT和TnI-肌动蛋白的交联产物，这表明在细肌丝复合物中，无论钙浓度如何，TnI都与TnC、TnT和肌动蛋白接触。未检测到TnI与原肌球蛋白之间的交联。发现钙会影响TnC-TnI和TnI-肌动蛋白的交联；当TnC被钙饱和时，TnC-TnI交联的程度增加，而TnI-肌动蛋白交联的程度降低。钙不影响TnI-TnT交联。
