Intestinal Basement Membrane of Ascaris suum

The Ascaris suum intestinal basement membrane was solubilized on reduction with P-mercaptoethanol in 1% sodium dodecyl sulfate and 1% sodium dodecyl sulfate, 8 M urea to the extent of 90% and lOO%, respectively. The reduced membrane consists of at least 17 polypeptides ranging in molecular weight from 22,500 to greater than 400,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography using 6 M urea as eluent. Six of these polypeptides contain carbohydrate, as determined by periodic acid-Schiff stain. Certain polypeptides, representing about 8% of the membrane by weight, are soluble in sodium dodecyl sulfate solutions without reduction and are not interlinked with each other by disulfide bonds; these interact in the membrane exclusively through noncovalent forces. Amino acid and carbohydrate analyses of the column fractions revealed that certain polypeptides are collagen-like, being greatly enriched in 4-hydroxyproline, hydroxylysine and glycine, and disaccharide units; whereas others are less collagen-like, being characterized by the absence of 4-hydroxyproline, low contents of hydroxylysine and glycine, and large contents of glutamic acid and proline, and enriched in oligosaccharide units. These results extend the observation from vertebrates to invertebrates that basement membranes consist of multiple polypeptides which have compositions of varying degrees of relatedness to collagen, suggesting a conservation of this structural characteristic during evolutionary development.