The Structure of F-actin Calculated from X-ray Fibre Diagrams and the 0.6 nm Crystal Structure

  • K. C. Holmes
  • D. Popp
  • W. Gebhard
  • W. Kabsch
Part of the Topics in Molecular and Structural Biology book series (TMSB)


The structure of the G-actin monomer complexed with DNase I has been solved by X-ray crystallography to a resolution of 0.6 nm (Figure 3.1; Suck et al., 1981). More recently the resolution has been increased to 0.45 nm and the actin molecule has been unambiguously identified (Kabsch et al., 1985). Work at present in progress in our laboratory has extended the resolution to 0.3 nm. This resolution has revealed the course of the chain in the actin monomer. Below, we describe the structure of F-actin arrived at by the following search procedure: the structure obtained from crystallography at 0.6 nm is placed in all possible orientations in the F-actin helix; the radius is adjusted to give the observed radius of gyration (2.5 nm: Hartt and Mendelson, 1980); the fibre diffraction pattern is computed from the resulting structure and compared with the X-ray diffraction data from oriented gels of F-actin (Popp et al., 1987) measured to 0.8 nm resolution. The intensity R-factor was used as an index of fit:
$$R = \frac{{\sum w{{\left( {{I_{calc}} - {I_{obs}}} \right)}^2}}}{{\sum w{I_{obs}}^2}}$$


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© The editor and contributors 1990

Authors and Affiliations

  • K. C. Holmes
  • D. Popp
  • W. Gebhard
  • W. Kabsch

There are no affiliations available

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