Surface layers (S-layers) comprise the outermost cell envelope component of most archaea and many bacteria. Here we present the structure of the bacterial S-layer protein SbsC from Geobacillus stearothermophilus, showing a very elongated and flexible molecule, with strong and specific binding to the secondary cell wall polymer (SCWP). The crystal structure of rSbsC(31-844) revealed a novel fold, consisting of six separate domains, which are connected by short flexible linkers. The N-terminal domain exhibits positively charged residues regularly spaced along the putative ligand binding site matching the distance of the negative charges on the extended SCWP. Upon SCWP binding, a considerable stabilization of the N-terminal domain occurs. These findings provide insight into the processes of S-layer attachment to the underlying cell wall and self-assembly, and also accommodate the observed mechanical strength, the polarity of the S-layer, and the pronounced requirement for surface flexibility inherent to cell growth and division. © 2008 Elsevier Ltd. All rights reserved.
Pavkov, T., Egelseer, E. M., Tesarz, M., Svergun, D. I., Sleytr, U. B., & Keller, W. (2008). The Structure and Binding Behavior of the Bacterial Cell Surface Layer Protein SbsC. Structure, 16(8), 1226–1237. https://doi.org/10.1016/j.str.2008.05.012