RELATIONSHIP BETWEEN MOIRE PATTERNS, TUBULIN SHAPE, AND MICROTUBULE POLARITY

The polarity of microtubules is reflected in cryo-electron microscope images and in three-dimensional reconstructions [Chretien 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 moire patients a nd the shape of the tubulin subunits are related. Microtubules observe d by cryo-electron microscopy show an arrowhead moire pattern that poi nts toward the plus end of microtubules with a right-handed protofilam ent skew and toward the minus end of microtubules with a left-handed p rotofilament skew. On the other hand, three-dimensional reconstruction s of microtubules observed from the plus end reveal a radial countercl ockwise slew of the tubulin subunits. We show how these polar features are related and present unambiguous rules for determining the polarit y on longitudinal and axial views of microtubules. (C) 1998 Wiley-Liss , Inc.