This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bingle, W H Articles by Baumeister, W Search for Related Content PubMed PubMed Citation Articles by Bingle, W H Articles by Baumeister, W

 Previous Article  |  Next Article 

J Bacteriol. 1987 November; 169(11): 5008-5015

Three-dimensional structure of the regular tetragonal surface layer of Azotobacter vinelandii.

Department of Microbiology, University of Alberta, Edmonton, Canada.

ABSTRACT

Fragments of the Azotobacter vinelandii tetragonal surface (S) layer, free of outer membrane material, were obtained by treating whole cells with 100 microM EDTA. The three-dimensional structure of the S layer was reconstructed from tilted-view electron micrographs of the S-layer fragments, after computer-assisted image processing by correlation averaging. At a resolution of 1.7 nm, the S layer exhibited funnel-shaped subunits situated at one fourfold-symmetry axis and interconnected at the other fourfold-symmetry axis to form prominent cruciform linking structures. These data, in conjunction with a relief reconstruction of the surface of freeze-etched whole cells, indicated that the apex of the funnel-shaped subunit was associated with the outer membrane, while the funnel "opening" faced the environment; the cruciform linking structures were formed at the outermost surface of the S layer. Electron microscopy and image enhancement were used to compare the structure of the outer membrane-associated S layer with that of fragments of the S layer dislodged from the outer membrane. This analysis revealed an increase in the lattice constant of the S layer from 12.5 to 13.6 nm and an alteration in the position of the cruciform linking structures in the z direction. These conformational changes resulted in a reduction in the thickness of the S layer (minimum estimate, 5 nm) and an apparent increase in the size of the gaps between the subunits. In terms of the porosity of the S layer, this gave the appearance of a transition from a closed to a more open structure.

This article has been cited by other articles:

• Candela, T., Mignot, T., Hagnerelle, X., Haustant, M., Fouet, A. (2005). Genetic analysis of Bacillus anthracis Sap S-layer protein crystallization domain. Microbiology 151: 1485-1490 [Abstract] [Full Text]