Flexibility within myosin heads revealed by negative stain and single-particle analysis

被引:40
作者
Burgess, SA
Walker, ML
White, HD
Trinick, J
机构
[1] UNIV BRISTOL,DEPT VET CLIN SCI,BRISTOL BS18 7DY,AVON,ENGLAND
[2] EASTERN VIRGINIA MED SCH,DEPT BIOCHEM,NORFOLK,VA 23507
关键词
D O I
10.1083/jcb.139.3.675
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Electron microscopy of negatively stained myosin has previously revealed three discrete regions within the heads of the molecule. However, despite a probable resolution of similar to 2 nm, it is difficult to discern directly consistent details within these regions. This is due to variability in both head conformation and in staining. In this study, we applied single-particle image processing and classified heads into homogeneous groups. The improved signal-to-noise ratio after averaging these groups reveals substantially improved detail. The image averages were compared to a model simulating negative staining of the atomic structure of subfragment-1 (S1). This shows that the three head regions correspond to the motor domain and the essential and regulatory light chains. The image averages were very similar to particular views of the S1 model. They also revealed considerable flexibility between the motor and regulatory domains, despite the molecules having been prepared in the absence of nucleotide. This flexibility probably results from rotation of the regulatory domain about the motor domain, where the relative movement of the regulatory light chain is up to 12 nm, and is most clearly illustrated in animated sequences (available at http://www.leeds.ac.uk/chb/muscle/myosinhead.html). The sharply curved conformation of the atomic model of S1 is seen only rarely in our data, with straighter heads being more typical.
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页码:675 / 681
页数:7
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