COUPLING BETWEEN THE ENZYMATIC SITE OF MYOSIN AND THE MECHANICAL OUTPUT OF MUSCLE
COUPLING BETWEEN THE ENZYMATIC SITE OF MYOSIN AND THE MECHANICAL OUTPUT OF MUSCLE
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DOI：
10.1016/0022-2836(79)90121-9
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发表时间：
1979-01-01
影响因子：
5.6
通讯作者：
CLARKE, ML
中科院分区：
文献类型：
--
作者：
MARSTON, SB;TREGEAR, RT;CLARKE, ML
当Mg-imido-ATP与甘油提取昆虫[Lethacerus cordofanus，L.]的肌球蛋白活性位点结合时。indicus和L. [灰肌]肌纤维，其引起每1/2肌节2nm的静止长度的快速、完全可逆和不依赖于应力的增加，而等张刚度保持在僵硬值的2%内。Mg-ADP和H-imido-ATP结合，但具有较小的机械效应，并且对赤道X射线衍射图案的影响也较小。结合到长度变化的耦合是定量可逆的，因为每个纤维200 nm的应力使低浓度下结合的Mg-酰亚胺-ATP或Mg-ATP的量加倍，但对Mg-ADP或H-酰亚胺-ATP结合没有影响。通过亚片段1在溶液中的研究表明了核苷酸和肌动蛋白结合位点之间的联系。用荧光滴定法测得亚片段1的核苷酸亲和力按H-亚氨基-ATP、Mg-ADP和Mg-imido-ATP的顺序增加，而用沉降法测得肌动蛋白对亚片段1的核苷酸亲和力按相同的顺序降低。的数据被解释在一个简单的跨桥模型和肌肉收缩的机制，它们的相关性进行了讨论。
When Mg-imido-ATP binds to the active site of myosin in glycerol-extracted insect [Lethacerus cordofanus, L. indicus and L. griseus] muscle fibers it causes a rapid, fully reversible and stress-independent increase in rest length of 2 nm per 1/2 sarcomere, while the isotonic stiffness remains within 2% of the rigor value. Mg-ADP and H-imido-ATP bind but have less mechanical effect and also less effect on the equatorial X-ray diffraction pattern. Coupling of binding to length change is quantitatively reversible, since stress of 200 nm per fiber doubles the amount of Mg-imido-ATP or Mg-ATP bound at low concentrations but has no effect on Mg-ADP or H-imido-ATP binding. Linkage between the nucleotide and actin binding sites is shown by studies with subfragment 1 in solution. By fluorometric titration the nucleotide affinity for subfragment 1 increased in the order of H-imido-ATP, Mg-ADP and Mg-imido-ATP, while by a sedimentation technique the affinity of actin for subfragment 1-nucleotide decreased in the same order. The data are interpreted in terms of a simple cross-bridge model and their relevance to the mechanism of muscle contraction is discussed.