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Updated: Aug 24, 2026

Directly Measuring Forces Within Reconstituted Active Microtubule Bundles
Published on: May 10, 2022
The pilus-retraction protein PilT: ultrastructure of the biological assembly
Katrina T Forest1, Kenneth A Satyshur, Gregory A Worzalla
1Department of Bacteriology, University of Wisconsin-Madison, USA. forest@bact.wisc.edu
Abstract:
PilT is a biological motor required for the retraction of bacterial type IV pili. Nesseria gonorrhoeae PilT has been purified and its ultrastructure has been examined by freeze-etch electron microscopy, revealing a 115 A outer diameter, 15-35 A inner diameter ring. Aquifex aeolicus PilT crystals were obtained in a primitive hexagonal space group (unit-cell parameters a = b = 107.3, c = 68.5 A) and diffract to a minimum Bragg spacing of 2.8 A when PilT is co-crystallized with adenine nucleotides. Initial phases to 3.5 A resolution have been determined by multiwavelength anomalous dispersion and density modification. Resulting electron-density maps show a hexameric A. aeolicus PilT ring 105 A wide by 55 A high, with an inner cavity that varies in shape and width from 20 to 40 A over the height of the complex. Both PilT ultrastructures are very similar to type II and type IV secretion ATPases in overall shape, size and assembly.
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