Intestinal mucin of germ-free rats. Biochemical and electron-microscopic characterization.

Purified germ-free rat intestinal mucin was found by chemical analysis to contain 25% protein, enriched in serine, threonine, and proline, 75% carbohydrate, and no nucleic acid. It was analyzed by darkfield electron microscopy and found to consist of long filamentous molecules with a maximum length of approximately 740 nm, a mean length of 456 nm, and a mean width of 7 nm. Given reasonable assumptions derived from earlier work on other well-characterized mucins, the molecular weight of the peptide, calculated by the length from electron microscopy, was 200,000, and, given the chemical composition, the molecular weight of the entire mucin molecule was calculated to be approximately 800,000.