Relationship between moiré patterns, tubulin shape, and microtubule polarity.
The polarity of microtubules is reflected in cryo-electron microscope images and in three-dimensional reconstructions [Chrétien et al., 1996: Structure 4:1031-1040; Sosa and Milligan, 1996: J. Mol. Biol. 260:743-755]. This paper shows how the directionality of the moiré patterns and the shape of the tubulin subunits are related. Microtubules observed by cryo-electron microscopy show an arrowhead moiré pattern that points toward the plus end of microtubules with a right-handed protofilament skew and toward the minus end of microtubules with a left-handed protofilament skew. On the other hand, three-dimensional reconstructions of microtubules observed from the plus end reveal a radial counterclockwise slew of the tubulin subunits. We show how these polar features are related and present unambiguous rules for determining the polarity on longitudinal and axial views of microtubules.
Sosa
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Department of Cell Biology MB25, The Scripps Research Institute, La Jolla, California, USA.
Chrétien
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D
D003198:Computer Simulation; D008870:Microtubules / Q000648:ultrastructure*; D015903:Moire Topography; D014404:Tubulin / Q000648:ultrastructure*
D014404:Tubulin