Identification and characterization of domains responsible for self-assembly and cell wall binding of the surface layer protein of Lactobacillus brevis ATCC 8287.
BACKGROUND
Lactobacillus brevis 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 Lactobacillus acidophilus group.


RESULTS
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 L. brevis 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 Lactobacillus acidophilus group S-layer proteins characterized so far. Conserved carbohydrate binding motifs were identified in the positively charged N-terminal regions of six Lactobacillus brevis S-layer proteins.


CONCLUSIONS
This study identifies SlpA as a two-domain protein in which the order of the functional domains is reversed compared to other characterized Lactobacillus S-layer proteins, and emphasizes the diversity of potential cell wall receptors despite similar carbohydrate binding sequence motifs in Lactobacillus S-layer proteins.
Avall-Jääskeläinen
Silja
S
Department of Basic Veterinary Sciences, Division of Microbiology and Epidemiology, University of Helsinki, Finland. silja.avall@helsinki.fi
Hynönen
Ulla
U
Ilk
Nicola
N
Pum
Dietmar
D
Sleytr
Uwe B
UB
Palva
Airi
A
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D002473:Cell Wall / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D005822:Genetic Vectors; D052196:Levilactobacillus brevis / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010957:Plasmids; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C070683:surface layer protein A, Bacteria