The Macrostructure of Mucus Glycoproteins in Solution

Abstract

This chapter describes the various models for mucus glycoprotein “macrostructure” (namely, assembly, gross conformation, and heterogeneity) in solution, which have been based on various interpretations of the data provided by various techniques. Native mucus secretions normally contain ∼1% of salts and other dialyzable components, 0.5%–1% of proteins, a similar proportion of carbohydrate-rich glycoprotein, and ∼95% of water. The molecular weights of mucus glycoproteins range from ∼0.5×106 to 16.0×106, and it is now widely accepted that the mucins of higher molecular weight are made up of the multiples of a basic unit having a molecular weight of (0.4–0.6) ×106. Although the electron-microscopic technique of air drying onto mica prior to platinum shadowing has yielded valuable information about the mode of assembly or secondary structure, it can yield misleading information about the gross conformation in solution. Selfassociation phenomena in solution do not appear to be significant, but bronchial mucins have been shown to interact with other components of mucus such as lysozyme and alginates.