Characterization of two different glycosylated domains from the insoluble mucin complex of rat small intestine.

• The highly glycosylated domains of rat small intestinal mucins were isolated after reduction and trypsin digestion and separated into two populations (A and B) by gel chromatography. The molecular mass values were 650 and 335 kDa, respectively, and the relative yields suggest that the two glycopeptides occur in equimolar proportions. Electron microscopy revealed linear structures with weight average lengths of 230 nm (A) and 110 nm (B) corresponding to a mass/unit length of about 3 kDa/nm. The protein cores (17-19%) contain large amounts of threonine (over 40%), serine (17-24%), and proline (18-19%). Carbohydrate and sulfate account for approximately 80 and 0.5%, respectively, and gas chromatography-mass spectrometry showed that the patterns of neutral and sialic acid-containing glycans are very similar in the two glycopeptides. Both contain a significant amount (7-10 mol %) of single GalNAc residues, the average oligosaccharide is about 4 sugar residues long, and the largest species observed are heptasaccharides. The major neutral and sialic acid-containing oligosaccharides are Fuc1-2Gal1-3GalNAcol and GlcNAc1-6(NeuGc2-Gal1-3)GalNAcol, respectively. Sialic acid is present as both N-acetyl- and N-glycoloyl-neuraminic acid. Repeated extractions of the tissue with guanidinium chloride left approximately 80% of the mucus glycoproteins as an insoluble glycoprotein complex whereas exposure to dithiothreitol or high speed homogenization accomplished complete solubilization. The "subunits" obtained after reduction with dithiothreitol are larger than glycopeptides A and B, and fragments corresponding in size to the latter are obtained after cleavage with trypsin. Most of the mucins from rat small intestine thus occurs as an insoluble glycoprotein complex composed of subunits joined with disulfide bonds. The subunits contain two highly glycosylated regions with different lengths substituted with very similar oligosaccharides.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinsk bioteknologi -- Medicinsk bioteknologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Medical Biotechnology -- Medical Biotechnology (hsv//eng)

Keyword

Amino Acids

analysis

Animals

Binding Sites

Carbohydrate Sequence

Centrifugation

Isopycnic

Glycopeptides

chemistry

isolation & purification

metabolism

Glycosylation

Guanidine

Guanidines

Intestinal Mucosa

chemistry

Intestine

Small

chemistry

Microscopy

Electron

Molecular Sequence Data

Molecular Weight

Mucins

chemistry

metabolism

N-Acetylneuraminic Acid

Oligosaccharides

analysis

chemistry

Rats

Rats

Sprague-Dawley

Sialic Acids

analysis

Publication and Content Type

ref (subject category)

art (subject category)