Nieznańska Hanna, Nieznański Krzysztof, Stepkowski Dariusz
Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warszawa, Poland.
Acta Biochim Pol. 2002;49(3):709-19.
In order to compare the ability of different isoforms of myosin essential light chain to interact with actin, the effect of the latter protein on the proteolytic susceptibility of myosin light chains (MLC-1S and MLC-1V - slow specific and same as ventricular isoform) from slow skeletal muscle was examined. Actin protects both slow muscle essential light chain isoforms from papain digestion, similarly as observed for fast skeletal muscle myosin (Nieznanska et al., 1998, Biochim. Biophys. Acta 1383: 71). The effect of actin decreases as ionic strength rises above physiological values for both fast and slow skeletal myosin, confirming the ionic character of the actin-essential light chain interaction. To better understand the role of this interaction, we examined the effect of synthetic peptides spanning the 10-amino-acid N-terminal sequences of myosin light chain 1 from fast skeletal muscle (MLC-1F) (MLCFpep: KKDVKKPAAA), MLC-1S (MLCSpep: KKDVPVKKPA) and MLC-1V (MLCVpep: KPEPKKDDAK) on the myofibrillar ATPase of fast and slow skeletal muscle. In the presence of MLCFpep, we observed an about 19% increase, and in the presence of MLCSpep about 36% increase, in the myofibrillar ATPase activity of fast muscle. On the other hand, in myofibrillar preparations from slow skeletal muscle, MLCSpep as well as MLCVpep caused a lowering of the ATPase activity by about 36%. The above results suggest that MLCSpep induces opposite effects on ATPase activity, depending on the type of myofibrils, but not through its specific N-terminal sequence - which differs from other MLC N-terminal peptides. Our observations lead to the conclusion that the action of different isoforms of long essential light chain is similar in slow and fast skeletal muscle. However the interaction of essential light chains with actin leads to different physiological effects probably depending on the isoforms of other myofibrillar proteins.
为了比较肌球蛋白必需轻链不同同工型与肌动蛋白相互作用的能力，研究了后者蛋白对慢肌骨骼肌中肌球蛋白轻链（MLC-1S和MLC-1V——慢肌特异性同工型且与心室同工型相同）蛋白水解敏感性的影响。肌动蛋白保护慢肌必需轻链两种同工型免受木瓜蛋白酶消化，这与在快肌骨骼肌肌球蛋白中观察到的情况类似（涅兹南斯卡等人，1998年，《生物化学与生物物理学报》1383:71）。对于快肌和慢肌骨骼肌，当离子强度升高到生理值以上时，肌动蛋白的作用减弱，这证实了肌动蛋白与必需轻链相互作用的离子特性。为了更好地理解这种相互作用的作用，我们研究了跨越快肌骨骼肌肌球蛋白轻链1（MLC-1F）（MLCFpep:KKDVKKPAAA）、MLC-1S（MLCSpep:KKDVPVKKPA）和MLC-1V（MLCVpep:KPEPKKDDAK）10个氨基酸N端序列的合成肽对快肌和慢肌骨骼肌肌原纤维ATP酶的影响。在存在MLCFpep的情况下，我们观察到快肌肌原纤维ATP酶活性增加了约19%，在存在MLCSpep的情况下增加了约36%。另一方面，在慢肌骨骼肌的肌原纤维制剂中，MLCSpep以及MLCVpep使ATP酶活性降低了约36%。上述结果表明，MLCSpep根据肌原纤维的类型对ATP酶活性产生相反的影响，但不是通过其特定的N端序列——该序列与其他MLC N端肽不同。我们的观察结果得出结论，长必需轻链不同同工型在慢肌和快肌骨骼肌中的作用相似。然而，必需轻链与肌动蛋白的相互作用可能导致不同的生理效应，这可能取决于其他肌原纤维蛋白的同工型。
