Identification and characterization of domains responsible for self-assembly and cell wall binding of the surface layer protein of <it>Lactobacillus brevis </it>ATCC 8287

• Main Authors: Sleytr Uwe B, Pum Dietmar, Ilk Nicola, Hynönen Ulla, Åvall-Jääskeläinen Silja, Palva Airi
• Format: Article
• Language: English
• Published: BMC 2008-10-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/8/165

<p>Abstract</p> <p>Background</p> <p><it>Lactobacillus brevis </it>ATCC 8287 is covered by a regular surface (S-) layer consisting of a 435 amino acid protein SlpA. This protein is completely unrelated in sequence to the previously characterized S-layer proteins of <it>Lactobacillus acidophilus </it>group.</p> <p>Results</p> <p>In this work, the self-assembly and cell wall binding domains of SlpA were characterized. The C-terminal self-assembly domain encompassed residues 179–435 of mature SlpA, as demonstrated by the ability of N-terminally truncated recombinant SlpA to form a periodic structure indistinguishable from that formed by full length SlpA. Furthermore, a trypsin degradation analysis indicated the existence of a protease resistant C-terminal domain of 214 amino acids. By producing a set of C-terminally truncated recombinant SlpA (rSlpA) proteins the cell wall binding region was mapped to the N-terminal part of SlpA, where the first 145 amino acids of mature SlpA alone were sufficient for binding to isolated cell wall fragments of <it>L. brevis </it>ATCC 8287. The binding of full length rSlpA to the cell walls was not affected by the treatment of the walls with 5% trichloroacetic acid (TCA), indicating that cell wall structures other than teichoic acids are involved, a feature not shared by the <it>Lactobacillus acidophilus </it>group S-layer proteins characterized so far. Conserved carbohydrate binding motifs were identified in the positively charged N-terminal regions of six <it>Lactobacillus brevis </it>S-layer proteins.</p> <p>Conclusion</p> <p>This study identifies SlpA as a two-domain protein in which the order of the functional domains is reversed compared to other characterized <it>Lactobacillus </it>S-layer proteins, and emphasizes the diversity of potential cell wall receptors despite similar carbohydrate binding sequence motifs in <it>Lactobacillus </it>S-layer proteins.</p>