Xu S, Yu L C, Schoenberg M
Laboratory of Physical Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Biophys J. 1998 Mar;74(3):1110-4. doi: 10.1016/S0006-3495(98)77829-4.
Using x-ray diffraction and mechanical stiffness, the response of N-phenylmaleimide (NPM)-reacted cross-bridges to solutions containing different amounts of ATP and Mg2+ has been studied. In relaxing solution containing greater than millimolar amounts of ATP and Mg2+, NPM-treated muscle fibers give x-ray diffraction patterns and stiffness records, which are nearly indistinguishable from those of untreated relaxed fibers. In a solution devoid of added ATP, but with Mg2+ (rigor(+Mg) solution), the muscle fibers still give x-ray diffraction patterns and mechanical responses characteristic of relaxed muscle. The new finding reported here is that in a solution devoid of both ATP and Mg2+ (rigor(-Mg) solution containing EDTA with no added ATP), NPM-reacted cross-bridges do give rigor-like behavior. This is the first report that NPM-reacted cross-bridges, at least in the presence of EDTA, are capable of going into a strongly binding conformation.
利用X射线衍射和机械刚度，研究了N-苯基马来酰亚胺（NPM）反应的横桥对含有不同量ATP和Mg2+的溶液的响应。在含有大于毫摩尔量ATP和Mg2+的松弛溶液中，经NPM处理的肌纤维给出的X射线衍射图谱和刚度记录，与未处理的松弛纤维几乎无法区分。在不含添加ATP但含有Mg2+的溶液（僵直（+Mg）溶液）中，肌纤维仍给出松弛肌肉特有的X射线衍射图谱和机械响应。此处报道的新发现是，在既不含ATP也不含Mg2+的溶液（不含添加ATP的含EDTA的僵直（-Mg）溶液）中，NPM反应的横桥确实表现出类似僵直的行为。这是首次报道NPM反应的横桥，至少在EDTA存在的情况下，能够进入强结合构象。
