The long term objectives are to understand the structure-function relationships and the biosynthesis and regulation of mucins as well as to obtain information on the role of mucins in disease. Mucins are believed to have a significant role in a variety of pathophysiologic processes including asthma, chronic bronchitis, cystic fibrosis, peptic ulcers, chronic gastritis, infertility and inflammatory bowel diseases. Mucins are rich in carbohydrate and the strong solvation property of the saccharides is thought to be a major factor in determining their viscoelastic, gel forming and lubricating properties. However, the nature of the polymeric structure of the mucins and the exact role of mucins in the formation of the mucus gel are poorly understood. In order to understand structure-function of these macromolecules we propose to continue our investigation of the subunit structure of bovine submaxillary mucin (BSM) using both biochemical and molecular biological techniques.
The specific aims are: 1. Isolate highly purified component glycoproteins of BSM and compare their protein composition and the profiles of the saccharides. 2. Prepare the core proteins of these glycoproteins by chemical and enzymatic deglycosylation and determine their structural similarities and differences by peptide mapping. 3. Sequence selected peptide fragments to further understand the structural relationship of the various components, to confirm or correct the primary sequence of these proteins deduced from the nucleotide sequence and, if appropriate, to generate polynucleotide probes. 4. Examine the interaction of the core proteins with the rabbit anti-apoBSM to investigate their immunological relationship. 5. Screen cDNA libraries from bovine submaxillary gland poly(A+) RNA using antibodies specific for the various core proteins to identify clones with cDNA sequences for the various mucin components. 6. Sequence the selected cDNA and genomic clones to deduce the primary amino acid sequence of the various components of BSM. These studies would provide information on the subunit structure of the glycoprotein components of BSM and the polymeric structure of this model mucin. This information would in turn contribute to our understanding of the more complex human tracheobronchial, gastrointestinal and urogenital mucins.