Arrangement of subunits in microtubules with 14 profilaments.

• DOI: 10.1083/jcb.87.2.521
• Publication Date: 2004-05-14T23:04:59Z
• Authors: G M Langford
• Keywords: Superhelix; Tubule

The structure of 14-protofilament microtubules reassembled from dogfish shark brain tubulin was analyzed by high resolution electron microscopy and optical diffraction. simultaneous imaging the protofilaments near far sides these tubules produces a moiré pattern with period approximately 96 nm. Optical diffraction patterns show that 5-nm spots arise for two tubule are not coincident but lie off equator distance 1/192 nm-1. These data provide evidence in containing 14 protofilaments, tilted 1.5 degrees respect to long axis tubule, giving left-handed superhelix pitch 2.7 micron. hypothesis is tilt occurs accommodate 14th protofilament. It determined when protofilament incorporated, 3-start helix maintained, angle changes 10.5 11.2 degrees, between measured center microtubule 2 dimer lattice discontinuous. observations molecule sufficiently flexible accomodate slight distortions at lateral bonding sites regions alpha beta monomers similar allow either alpha-alpha beta-beta subunit pairing or alpha-beta pairing.