The cell envelope of Thermoproteus tenax : three-dimensional structure of the surface layer and its role in shape maintenance

Abstract

The sulphur-dependent archaebacterium Thermoproteus tenax has a cylindrical cell shape variable in length, but constant in diameter. Its whole surface is covered by a regular protein layer (S-layer). The lattice has p6 symmetry and a lattice constant of 32.8 nm. The three-dimensional reconstruction from a tilt series of isolated and negatively stained S-layer shows a complex mass distribution of the protein: a prominent, pillar-shaped protrusion is located at the 6-fold crystallographic axis with radiating arms connecting neighbouring hexamers in the vicinity of the 3-fold axis. The base vectors of the S-layer lattice have a preferred orientation with respect to the longitudinal axis of the cell. The layer can be seen as a helical structure consisting of a right-handed, two-stranded helix, with the individual chains running parallel. Supposing that new S-layer protein is inserted at lattice faults (wedge disclinations) near the poles, growing of the layer would then proceed by moving a discination at the end of the helix. The constant shape of the cell, as well as the particular structure of the layer, strongly suggest that this S-layer has a shape-maintaining function.

A general strategy for identification of S-layer genes in the Bacillus cereus group: molecular characterization of such a gene in Bacillus thuringiensis subsp. galleriae NRRL 4045 The GenBank accession number for the slpA sequence is AJ249446.

“…For cloning experiments, plasmids pUC19, pNEB193 and pQE30 were routinely used (Yanisch-Perron et al, 1985 ;New England Laboratories ;Qiagen). For mating experiments, DNA fragments were inserted into pAT113 (Trieu-Cuot et al, 1991).…”

“…Few data are available concerning the function of S-layers. Nevertheless, some studies have shown that the S-layer is involved in cell integrity and shape maintenance in S. MESNAGE, M. HAUSTANT and A. FOUET archaea, in which it is often the only cell-envelope component (Mescher & Strominger, 1976 ;Wildhaber & Baumeister, 1987). In some pathogenic bacteria, the S-layer is involved in resistance to complement-mediated killing or interaction with host cells and molecules (Pei & Blaser, 1990 ;Kotiranta et al, 1998).…”

The S‐layer protein of Corynebacterium glutamicum is anchored to the cell wall by its C‐terminal hydrophobic domain

“…They probably act as protective coats, molecular sieves or ion traps (for a review, see Beveridge and Graham, 1991;Messner and Sleytr, 1992). In Archaebacteria, they determine and maintain cell shape (Mescher and Strominger, 1976;Wildhaber and Baumeister, 1987). In some cases, S-layers were also identified as virulence factors (Evenberg and Lugtenberg, 1982;Fujimoto et al, 1991;Wang et al, 1993).…”

S layer regeneration in Methanococcus voltae protoplasts

“…Archaeal cell envelopes often consist solely of a paracrystalline protein monolayer (S layer) (reviewed by Messner & Sleytr, 1992) which is in peripheral contact with the outer face of the plasma On: Fri, 11 May 2018 19:18:02 M. FIRTEL, G. B. PATEL a n d T. J. BEVERIDGE membrane (PM) (Konig, 1988). Archaeal S layers contact the PM via inner surface extensions which probably embed in the hydrophobic region of the PM (Hovmoller et al, 1988;Baumeister et al, 1989;Wildhaber & Baumeister, 1987;Phipps e t al., 1990;Firtel et al, 1993). The S layer is formed from a single type of interlocking polypeptide bound together by noncovalent forces, and is structured to produce transversing channels that are apparent in negative stain transmission electron microscopy (TEM) (Hovmoller et al ,1988) and in ultrafiltration assays (Sira & Sleytr, 1987a).…”