title: Identification of two major populations of mucins in respiratory secretions.
abstract: Two populations of reduced subunits were present in the mucins purified from pooled normal secretions and asthmatic and chronic bronchitic sputa; their relative level differed between samples. To investigate the nature of this heterogeneity, an asthmatic respiratory mucin preparation from a single individual was reduced and alkylated with 14C-iodoacetamide. This preparation was analyzed by gel filtration, agarose gel electrophoresis, immunoblotting, rate-zonal- and density-gradient centrifugation, and HPLC ion-exchange- and reverse-phase chromatography. Two populations (A and B) of reduced mucin subunits and a high-M(r)protein-rich fraction were identified. Species A has the higher molecular mass, is slowest migrating on agarose electrophoresis, has longer oligosaccharide chains, and expresses the carbohydrate structure sialyl-Le(x). Species B has a lower molecular mass, migrates faster in agarose electrophoresis Species B has a lower molecular mass, migrates faster in agarose electrophoresis, has shorter chains, and does not express sialyl-Le(x). The two subunits have similar but not identical amino acid compositions and 14C-tryptic peptide maps indicating they have different protein cores. The anti-sialyl-Le(x) antibody selectively precipitated subunit A not only from the reduced but also from the nonreduced mucin preparation, demonstrating that subunits A and B are present in different intact mucins.
authors.affiliation: Division of Biochemistry, School of Biological Sciences, University of Manchester, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Thornton
authors.forename: P L
authors.initials: PL
authors.lastname: Devine
authors.forename: C
authors.initials: C
authors.lastname: Hanski
authors.forename: M
authors.initials: M
authors.lastname: Howard
authors.forename: J K
authors.initials: JK
authors.lastname: Sheehan
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001249:Asthma / Q000378:metabolism; D001991:Bronchitis / Q000378:metabolism; D002908:Chronic Disease; D006801:Humans; D008722:Methods; D008854:Microscopy, Electron; D008970:Molecular Weight; D009005:Monosaccharides / Q000032:analysis; D009077:Mucins / Q000032:analysis* / Q000302:isolation & purification / Q000648:ultrastructure; D009093:Mucus / Q000737:chemistry*; D012016:Reference Values; D013183:Sputum / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D009005:Monosaccharides; D009077:Mucins