Fei S, Yamanoue M, Okayama T
Graduate School of Science and Technology, Faculty of Agriculture, Kobe University, Japan.
Biosci Biotechnol Biochem. 1999 Aug;63(8):1425-32. doi: 10.1271/bbb.63.1425.
The binding of paratropomyosin to beta-connectin, which has been suggested to interact at the A-I junction of a sarcomere, was confirmed by measuring the changes in turbidity of a mixture with changing NaCl concentration, pH and free calcium ions, and by morphological observation and a coprecipitation assay of the aggregates formed in the mixture. Paratropomyosin also bound to the 400-kDa fragment which is the N-terminal portion of beta-connectin and contains the A-I junction region. Moreover, the interaction of paratropomyosin with the 400-kDa fragment was enhanced by a calcium ion concentration from 10(-7) M to 10(-5) M and markedly suppressed above 10(-4) M calcium ions. We conclude that paratropomyosin probably binds to the 400-kDa fragment of beta-connectin in the A-I junction region in living and pre-rigor skeletal muscle. In postmortem skeletal muscle paratropomyosin may be released from the 400-kDa portion of the connectin filament by increased calcium ion concentration and translocated on to thin filaments to induce meat tenderization.
副肌球蛋白与β-连接蛋白的结合已被证实，有人提出它们在肌节的A-I连接处相互作用，通过测量随着氯化钠浓度、pH值和游离钙离子变化的混合物的浊度变化，以及通过形态学观察和对混合物中形成的聚集体的共沉淀分析来证实。副肌球蛋白也与400 kDa片段结合，该片段是β-连接蛋白的N端部分，包含A-I连接区域。此外，钙离子浓度从10^(-7) M增加到10^(-5) M时，副肌球蛋白与400 kDa片段的相互作用增强，而在钙离子浓度高于10^(-4) M时则明显受到抑制。我们得出结论，在活体和僵硬前的骨骼肌中，副肌球蛋白可能在A-I连接区域与β-连接蛋白的400 kDa片段结合。在死后骨骼肌中，副肌球蛋白可能因钙离子浓度增加而从连接蛋白丝的400 kDa部分释放出来，并转移到细肌丝上以诱导肉的嫩化。
