Komatsu H, Tawada K
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
J Biol Chem. 1993 Aug 15;268(23):16974-8.
A molecule of myosin subfragment 1 (S1) from rabbit skeletal muscle has one highly reactive lysine residue, Lys-83 (RLR), in the heavy chain, which is rapidly and stoichiometrically modified by trinitrobenzenesulfonate. Our previous kinetic study (Komatsu, H., Emoto, Y., and Tawada K. (1993) J. Biol. Chem. 268, 7799-7808) showed that although MgPPi reduces the maximum number of trinitrophenylated RLR down to about 0.5 mol/mol of S1, this half-stoichiometric modification of RLR is not the result of any heterogeneity in the primary structure of S1. However, this result conflicts with a previous report in which the half-stoichiometric trinitrophenylation has been reported to be related to Pro/Ser microheterogeneity at the 78th residue position in the heavy chain of rabbit skeletal muscle myosin. To resolve the conflict, we isolated peptides containing both the 78th residue and RLR from the two different preparations of S1, one whose RLR was trinitrophenylated in the presence of MgPPi and the other whose RLR was not trinitrophenylated in the presence of MgPPi, and then we determined the amino acid sequences of the peptides. We found the same Pro/Ser microheterogeneity at the 78th position in the peptides from these S1s and thus concluded that this microheterogeneity has no correlation to the half-stoichiometric trinitrophenylation of RLR.
来自兔骨骼肌的肌球蛋白亚片段1（S1）分子在重链中有一个高反应性赖氨酸残基，即Lys-83（RLR），它能被三硝基苯磺酸快速且化学计量地修饰。我们之前的动力学研究（小松，H.，江本，Y.，和田田，K.（1993）《生物化学杂志》268，7799 - 7808）表明，尽管MgPPi能将三硝基苯化的RLR的最大数量降低至约0.5摩尔/摩尔的S1，但RLR的这种半化学计量修饰并非S1一级结构中任何异质性的结果。然而，这一结果与之前的一份报告相冲突，在那份报告中，半化学计量的三硝基苯化被报道与兔骨骼肌肌球蛋白重链第78位残基处的脯氨酸/丝氨酸微异质性有关。为了解决这一冲突，我们从两种不同的S1制剂中分离出包含第78位残基和RLR的肽段，一种其RLR在MgPPi存在下被三硝基苯化，另一种其RLR在MgPPi存在下未被三硝基苯化，然后我们测定了这些肽段的氨基酸序列。我们在来自这些S1的肽段的第78位发现了相同的脯氨酸/丝氨酸微异质性，因此得出结论，这种微异质性与RLR的半化学计量三硝基苯化无关。
