期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1998
卷号：95
期号：6
页码：2944-2949
DOI：10.1073/pnas.95.6.2944
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：For more than 30 years, the fundamental goal in molecular motility has been to resolve force-generating motor protein structural changes. Although low-resolution structural studies have provided evidence for force-generating myosin rotations upon muscle activation, these studies did not resolve structural states of myosin in contracting muscle. Using electron paramagnetic resonance, we observed two distinct orientations of a spin label attached specifically to a single site on the light chain domain of myosin in relaxed scallop muscle fibers. The two probe orientations, separated by a 36{degrees} {+/-} 5{degrees} axial rotation, did not change upon muscle activation, but the distribution between them changed substantially, indicating that a fraction (17% {+/-} 2%) of myosin heads undergoes a large (at least 30{degrees}) axial rotation of the myosin light chain domain upon force generation and muscle contraction. The resulting model helps explain why this observation has remained so elusive and provides insight into the mechanisms by which motor protein structural transitions drive molecular motility.
