SclC is a member of a novel family of collagen-like proteins in Streptococcus equi subspecies equi that are recognised by antibodies against SclC

Previously we have reported on a cell surface collagen-like protein, called ScIC, from Streptococcus equi subspecies equi. In the present study we show that this protein is a member of a family of seven collagen-like proteins, called ScIC-ScII in this subspecies. All proteins contain an N-terminal signal sequence, followed by a unique non-repetitive region called A, a highly repetitive collagen-like region (CL) consisting of Glycine-Xaa-Yaa-triplet repeats. Following the CL-region a C-terminal proline-rich putative wall spanning region (W) preceding an LPXTG-motif and a hydrophobic transmembrane region (M) are found, typical features of cell surface exposed proteins in Gram-positive bacteria. The nucleotide and amino acid sequences, were analysed to investigate the similarities between them, and recombinant proteins encoding different domains (A- and CL-regions) were expressed and purified. Although the novel collagen-like proteins display differences in amino acid sequences, affinity purified antibodies against ScIC were found to cross react with the other members of the novel collagen-like proteins. Furthermore, in sera from horses previously diagnosed having strangles, antibodies against these proteins were detected suggesting that these proteins are expressed during the infection. (c) 2005 Elsevier B.V All rights reserved.