This is again somewhat surprising since EF-Tu, in general, is an intracellular protein that promotes the GTP-dependent binding of aminoacyl-tRNA to the a-site of ribosomes during protein biosynthesis [43]. However, there are several reports that some intracellular proteins, including Ganetespib solubility dmso elongation factors EF-G, EF-Ts, EF-P, and EF-Tu, can be localized on the cell surface of the pathogens and interact

with extracellular proteins [39, 41, 44, 45]. Furthermore, it has been demonstrated in a previous study that elongation factor Tu (Ef-Tu) from Lactobacillus johnsonii is the main cell surface protein that mediates its binding to intestinal epithelial cells and mucins [46]. Expression of cell surface lipoproteins of Streptococcus gordonii is related to its adherence and coaggregation [22]. It has been shown previously that the 76 kDa lipoprotein, termed SarA (hppA) from S. gordonii is a crucial cell surface protein that enables the bacteria to aggregate

and coaggregate with certain microorganisms [23]. Here, we have clearly identified that the 78 kDa putative MUC7-binding band contains the hppA gene product, oligopeptide binding lipoprotein. This cell surface lipoprotein has been shown to be essential for uptake of hexa- and heptapeptides as source of SHP099 in vivo nutrients to the organism Selleckchem Momelotinib [47]. Our results indicate that MUC7 binds to this lipoprotein adhesin; possibly this binding hinders the lipoproteins function in nutrient uptake and preventing adhesion and aggregation Phospholipase D1 to the mucosal and/or dental surfaces. Detergent extraction of surface proteins from different streptococcal species has been successfully applied to study different aspects of their surface proteins, including identifying mucin binding adhesins [48, 49]. In the current study, extraction of streptococcal cell surface proteins was achieved by SDS, which has been used previously to extract lipoprotein adhesins from S. gordonii

[47, 50]. The SDS-PAGE profiles of the SDS extracted proteins observed here are in general agreement with published data [51]. In order to identify MUC7 binding proteins from S. gordonii, a blot overlay assay was employed. This method has been successfully employed to investigate mucin-bacteria interactions by various investigators [22, 44, 46]. For example, Murray et al. [52] demonstrated that detergent-extracted S. gordonii surface proteins were able to bind a trisaccharide that is later shown as a major oligosaccharide structure on MUC7 [53]. Furthermore, Carnoy et al. [54] used a similar strategy that was employed here (western blotting of extracted bacterial protein and subsequent probing with mucins) to identify Pseudomonas aeruginosa outer membrane adhesins that bind respiratory mucins. However, none of these studies have identified the specific bacterial proteins that bind to the mucins.