Biophysical characterization of mucin components HTM-1 and HTM-2 from tracheobronchial secretions of cystic fibrosis patients.

Mucins present in the tracheobronchial secretions are responsible for the viscoelastic properties of the mucus. Any changes in the mucin structure may alter the physical properties of mucus and hence its function. Previous studies from this laboratory have reported the isolation and characterization of a major mucin component (HTM-1) and a minor, novel mucin component (HTM-2) from the tracheobronchial secretions of cystic fibrosis (CF) individuals. In the present study, the macromolecular properties of the CF mucin components HTM-1 and HTM-2 were further investigated using biophysical methods. Dynamic light scattering studies showed that CF HTM-1 and HTM-2 had a greater extended structure in buffer containing 0.10 and 0.15 M NaCl than that observed in the presence of 0.03 M NaCl. Also, CF HTM-1 had a compact configuration in the presence of 5 and 10 mM Ca2+, while under similar experimental conditions, the structure of CF HTM-2 was unaffected, indicating differences in the macromolecular properties of CF mucin components. Fluorescent probe binding studies revealed that CF HTM-1 had more hydrophobic probe binding domains than those observed for CF HTM-2. In summary, both biochemical and biophysical characterization suggests structural differences between the CF HTM-1 and HTM-2 components.