Mucins are the major glycoproteins of human submandibular- sublingual saliva and tracheobronchial secretions. In the past decade, specific interactions between Pseudomonas aeruginosa and salivary and tracheobronchial mucins have been identified. These interactions may play an important role in bacterial pathogenesis. The long range goal of this project is to understand the pathogenesis of respiratory infections, and in particular the role of salivary and tracheobronchial mucins in this process. This will be studied by the characterization of the interactions between bacterial adhesions and mucins; receptors from healthy individuals and those with disease, for example cystic fibrosis (CF). An understanding of the mechanism of respiratory pathogens-salivary/tracheobronchial mucin interactions may provide a strategy to protect against pneumonias. Recent studies from our laboratory, indicated a protein to protein interaction between a 16 kDa component of P.aeruginosa and the peptide moiety of tracheobronchial mucin. A protein to protein interaction was also identified between pili of P. aeruginosa and the peptide moiety of a lower-molecular-weight salivary mucin (MG2). A higher-molecular-weight salivary mucin (MG1) has also been found to bind to a 16 kDa component of P. aeruginosa. In this applications, we propose to characterize the P. aeruginosa adhesins for salivary and tracheobronchial mucins from normal individuals, and salivary mucins' receptors for P. aeruginosa.
The specific aims are: 1. Characterization of a nonpilus protein adhesin of P. aeruginosa for human tracheobronchial mucin (HTBM)- We have identified a 16 kDa nonpilus protein component from the PBS extract of P. aeruginosa as an adhesin for HTBM of a normal individual. Preliminary data suggests that the adhesin may be located on the bacterial surface. This will be confirmed by immunolocalization. Preliminary studies indicate that the binding domain in the adhesin may be located at or around lysine and arginine. We will attempt to identify these binding sites by employing appropriate proteolytic and synthetic fragments of the bacterial component in the binding assays. The required amino acid sequence of the 16kDa component will be derived by recombinant DNA technology. 2. Characterization of the binding domains in MG2, and pili of P. aeruginosa- We have demonstrated that pili are adhesins for MG2. The binding between the two appears to be a protein to protein interaction and may involve hydrophobic domains. Utilizing appropriate (glyco)peptides of MG2 and pili, we will attempt to identify the binding domains. 3. Characterization of interactions between MG1 and P. aeruginosa- MG1 was also found to bind to a 16kDa component of P. aeruginosa. Initially, studies will be focused on determining if the 16 kDa component, that binds MG1, is same as the one that binds HTBM. We will then attempt to determine whether a common mechanism exists for binding of P. aeruginosa to HTBM, and MG1 by employing purified 16 kDa component and proteolytic and synthetic fragments from Specific Aim 1 in the binding assays.
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