Molecular and genomic analysis of genes encoding surface-anchored proteins from Clostridium difficile - PubMed (original) (raw)

Molecular and genomic analysis of genes encoding surface-anchored proteins from Clostridium difficile

T Karjalainen et al. Infect Immun. 2001 May.

Abstract

The gene slpA, encoding the S-layer precursor protein in the virulent Clostridium difficile strains C253 and 79--685, was identified. The precursor protein carries a C-terminal highly conserved anchoring domain, similar to the one found in the Cwp66 adhesin (previously characterized in strain 79--685), an SLH domain, and a variable N-terminal domain mediating cell adherence. The genes encoding the S-layer precursor proteins and the Cwp66 adhesin are present in a genetic locus carrying 17 open reading frames, 11 of which encode a similar two-domain architecture, likely to include surface-anchored proteins.

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Figures

FIG. 1

FIG. 1

(A) Diagram of the domain structure of the protein SlpA: a potential leader peptide (black box) is followed by the SLH domain and two larger domains named N and C. The numbers refer to amino acid positions in the protein. The regions corresponding to the P36 and P47 S-layer proteins of C. difficile strain C253 are indicated, as are the positions of repeat sequences (arrows). (B) Alignment of the repeats of the SlpA protein in the C-terminal domain. The length of the C-terminal repeats is between 85 and 111 amino acids. The amino acid positions in the SlpA protein are indicated. ∗ and +, two and three identical amino acids, respectively; ○ and !, two and three functionally identical amino acids (A, S, and T; D and E; N and Q; R and K; I, L, M, and V; F, Y, and W), respectively.

FIG. 2

FIG. 2

(A) Amino acid sequence alignment of the N-terminal domains of SlpA from three C. difficile strains, C253, 630, and 79–685. Note the pronounced variability. The SLH domain is shaded in gray; the conserved residues of this domain (12) are in boldface letters. Asterisks or colons denote amino acids that are identical or similar, respectively. The positions of the two peptides of C. difficile C253 (Table 1) are marked above the sequence. The N-terminal amino acids of the P36 and P47 proteins are indicated with arrows. (B) Amino acid sequence alignment of the putative cell wall-anchoring domains of SlpA and Cwp66 from C. difficile strains 630 and C253 and strain 79–685. Asterisks or colons denote amino acids that are identical or similar, respectively, in the SlpA proteins only. Conserved residues in the four proteins are in boldface.

FIG. 3

FIG. 3

Genetic organization of a 37-kb DNA fragment carrying the slpA and cwp66 genes from the genome of C. difficile 630. The proteins encoded by these genes and their sizes, molecular masses, and domain structures are indicated. Orf7 exhibits significant homology with the SecA protein from B. subtilis, Orf9 with dehydrogenases, Orf12 with _N_-acetyl-

l

-alanine-muramyl amidase, and Orf13 with glycosyltransferases. A.A., amino acids.

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