Electron microscopy and x-ray diffraction evidence for two Z-band structural states.

Published

Journal Article

In vertebrate muscles, Z-bands connect adjacent sarcomeres, incorporate several cell signaling proteins, and may act as strain sensors. Previous electron microscopy (EM) showed Z-bands reversibly switch between a relaxed, "small-square" structure, and an active, "basketweave" structure, but the mechanism of this transition is unknown. Here, we found the ratio of small-square to basketweave in relaxed rabbit psoas muscle varied with temperature, osmotic pressure, or ionic strength, independent of activation. By EM, the A-band and both Z-band lattice spacings varied with temperature and pressure, not ionic strength; however, the basketweave spacing was consistently 10% larger than small-square. We next sought evidence for the two Z-band structures in unfixed muscles using x-ray diffraction, which indicated two Z-reflections whose intensity ratios and spacings correspond closely to the EM measurements for small-square and basketweave if the EM spacings are adjusted for 20% shrinkage due to EM processing. We conclude that the two Z-reflections arise from the small-square and basketweave forms of the Z-band as seen by EM. Regarding the mechanism of transition during activation, the effects of Ca(2+) in the presence of force inhibitors suggested that the interconversion of Z-band forms was correlated with tropomyosin movement on actin.

Full Text

Duke Authors

Cited Authors

  • Perz-Edwards, RJ; Reedy, MK

Published Date

  • August 3, 2011

Published In

Volume / Issue

  • 101 / 3

Start / End Page

  • 709 - 717

PubMed ID

  • 21806939

Pubmed Central ID

  • 21806939

Electronic International Standard Serial Number (EISSN)

  • 1542-0086

Digital Object Identifier (DOI)

  • 10.1016/j.bpj.2011.06.024

Language

  • eng

Conference Location

  • United States