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Biochem J. Mar 1, 1999; 338(Pt 2): 507–513.
PMCID: PMC1220079

Physical characterization of a low-charge glycoform of the MUC5B mucin comprising the gel-phase of an asthmatic respiratory mucous plug.


We have previously noted that sequential extraction of an asthmatic mucous exudate with 6 M guanidinium chloride yielded a fraction of the mucins that were most resistant to solubilization and of high Mr [Sheehan, Richardson, Fung, Howard and Thornton (1995) Am. J. Respir. Cell Mol. Biol. 13, 748-756]. Here we show that this mucin fraction is dominated (at least 96% of the total) by the low-charge glycoform of the MUC5B gene product. Seen in the electron microscope the mucins appeared mainly as compact 'island' structures composed of linear threads often emanating from globular 'nodes' rather than the discrete linear threads more typical of mucins that we have previously described. The effect of reducing agents was as expected for other gel-forming mucins, i.e. reduced subunits or monomers of Mr 3x10(6)) were produced within 15 min of treatment. Kinetic experiments on the cleavage of the intact mucins with the proteinase trypsin indicated two clear regimes of fragmentation. An initial rapid cleavage generated mucins ranging from Mr=4x10(6) to 30x10(6) that in the electron microscope appeared as polydisperse threads (500-3000 nm in length), similar to normal and other respiratory mucins that we have previously characterized. A subsequent slower fragmentation over many hours yielded a major fragment of Mr 3x10(6) and length 200-600 nm, very similar in size and Mr to the subunits obtained by reduction. The results suggest that the MUC5B mucin is assembled, first into polydisperse linear threads, which are then linked together via a protein-mediated process. This might involve part of the mucin polypeptide or an as yet unidentified protein(s). The high proteinase susceptibility of the linkage suggests that it might be a point of control for mucin size and thus mucus rheology.

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Selected References

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  • Sheehan JK, Richardson PS, Fung DC, Howard M, Thornton DJ. Analysis of respiratory mucus glycoproteins in asthma: a detailed study from a patient who died in status asthmaticus. Am J Respir Cell Mol Biol. 1995 Dec;13(6):748–756. [PubMed]
  • Gupta R, Jentoft N, Jamieson AM, Blackwell J. Structural analysis of purified human tracheobronchial mucins. Biopolymers. 1990 Feb 5;29(2):347–355. [PubMed]
  • Gupta R, Jentoft N. The structure of tracheobronchial mucins from cystic fibrosis and control patients. J Biol Chem. 1992 Feb 15;267(5):3160–3167. [PubMed]
  • Thornton DJ, Davies JR, Kraayenbrink M, Richardson PS, Sheehan JK, Carlstedt I. Mucus glycoproteins from 'normal' human tracheobronchial secretion. Biochem J. 1990 Jan 1;265(1):179–186. [PMC free article] [PubMed]
  • Thornton DJ, Sheehan JK, Lindgren H, Carlstedt I. Mucus glycoproteins from cystic fibrotic sputum. Macromolecular properties and structural 'architecture'. Biochem J. 1991 Jun 15;276(Pt 3):667–675. [PMC free article] [PubMed]
  • Thornton DJ, Devine PL, Hanski C, Howard M, Sheehan JK. Identification of two major populations of mucins in respiratory secretions. Am J Respir Crit Care Med. 1994 Sep;150(3):823–832. [PubMed]
  • Davies JR, Hovenberg HW, Lindén CJ, Howard R, Richardson PS, Sheehan JK, Carlstedt I. Mucins in airway secretions from healthy and chronic bronchitic subjects. Biochem J. 1996 Jan 15;313(Pt 2):431–439. [PMC free article] [PubMed]
  • Slayter HS, Lamblin G, Le Treut A, Galabert C, Houdret N, Degand P, Roussel P. Complex structure of human bronchial mucus glycoprotein. Eur J Biochem. 1984 Jul 16;142(2):209–218. [PubMed]
  • Marianne T, Perini JM, Lafitte JJ, Houdret N, Pruvot FR, Lamblin G, Slayter HS, Roussel P. Peptides of human bronchial mucus glycoproteins. Size determination by electron microscopy and by biosynthetic experiments. Biochem J. 1987 Nov 15;248(1):189–195. [PMC free article] [PubMed]
  • Gum JR, Jr, Hicks JW, Toribara NW, Siddiki B, Kim YS. Molecular cloning of human intestinal mucin (MUC2) cDNA. Identification of the amino terminus and overall sequence similarity to prepro-von Willebrand factor. J Biol Chem. 1994 Jan 28;269(4):2440–2446. [PubMed]
  • Meezaman D, Charles P, Daskal E, Polymeropoulos MH, Martin BM, Rose MC. Cloning and analysis of cDNA encoding a major airway glycoprotein, human tracheobronchial mucin (MUC5). J Biol Chem. 1994 Apr 29;269(17):12932–12939. [PubMed]
  • Desseyn JL, Aubert JP, Van Seuningen I, Porchet N, Laine A. Genomic organization of the 3' region of the human mucin gene MUC5B. J Biol Chem. 1997 Jul 4;272(27):16873–16883. [PubMed]
  • Desseyn JL, Guyonnet-Dupérat V, Porchet N, Aubert JP, Laine A. Human mucin gene MUC5B, the 10.7-kb large central exon encodes various alternate subdomains resulting in a super-repeat. Structural evidence for a 11p15.5 gene family. J Biol Chem. 1997 Feb 7;272(6):3168–3178. [PubMed]
  • Keates AC, Nunes DP, Afdhal NH, Troxler RF, Offner GD. Molecular cloning of a major human gall bladder mucin: complete C-terminal sequence and genomic organization of MUC5B. Biochem J. 1997 May 15;324(Pt 1):295–303. [PMC free article] [PubMed]
  • Toribara NW, Ho SB, Gum E, Gum JR, Jr, Lau P, Kim YS. The carboxyl-terminal sequence of the human secretory mucin, MUC6. Analysis Of the primary amino acid sequence. J Biol Chem. 1997 Jun 27;272(26):16398–16403. [PubMed]
  • Voorberg J, Fontijn R, Calafat J, Janssen H, van Mourik JA, Pannekoek H. Assembly and routing of von Willebrand factor variants: the requirements for disulfide-linked dimerization reside within the carboxy-terminal 151 amino acids. J Cell Biol. 1991 Apr;113(1):195–205. [PMC free article] [PubMed]
  • Ruggeri ZM, Ware J. von Willebrand factor. FASEB J. 1993 Feb 1;7(2):308–316. [PubMed]
  • Thornton DJ, Carlstedt I, Howard M, Devine PL, Price MR, Sheehan JK. Respiratory mucins: identification of core proteins and glycoforms. Biochem J. 1996 Jun 15;316(Pt 3):967–975. [PMC free article] [PubMed]
  • Thornton DJ, Howard M, Khan N, Sheehan JK. Identification of two glycoforms of the MUC5B mucin in human respiratory mucus. Evidence for a cysteine-rich sequence repeated within the molecule. J Biol Chem. 1997 Apr 4;272(14):9561–9566. [PubMed]
  • Wickström C, Davies JR, Eriksen GV, Veerman EC, Carlstedt I. MUC5B is a major gel-forming, oligomeric mucin from human salivary gland, respiratory tract and endocervix: identification of glycoforms and C-terminal cleavage. Biochem J. 1998 Sep 15;334(Pt 3):685–693. [PMC free article] [PubMed]
  • Thornton DJ, Holmes DF, Sheehan JK, Carlstedt I. Quantitation of mucus glycoproteins blotted onto nitrocellulose membranes. Anal Biochem. 1989 Oct;182(1):160–164. [PubMed]
  • Thornton DJ, Howard M, Devine PL, Sheehan JK. Methods for separation and deglycosylation of mucin subunits. Anal Biochem. 1995 May 1;227(1):162–167. [PubMed]
  • Sheehan JK, Carlstedt I. The effect of guanidinium chloride on the behaviour of human cervical-mucus glycoproteins. Evidence for unfolding regions of ordered structure in 6M-guanidinium chloride. Biochem J. 1984 Jul 15;221(2):499–504. [PMC free article] [PubMed]
  • Mould AP, Holmes DF, Kadler KE, Chapman JA. Mica sandwich technique for preparing macromolecules for rotary shadowing. J Ultrastruct Res. 1985 Apr;91(1):66–76. [PubMed]
  • Carlstedt I, Lindgren H, Sheehan JK. The macromolecular structure of human cervical-mucus glycoproteins. Studies on fragments obtained after reduction of disulphide bridges and after subsequent trypsin digestion. Biochem J. 1983 Aug 1;213(2):427–435. [PMC free article] [PubMed]
  • Rose MC, Voter WA, Brown CF, Kaufman B. Structural features of human tracheobronchial mucus glycoprotein. Biochem J. 1984 Sep 1;222(2):371–377. [PMC free article] [PubMed]
  • Rose MC, Kaufman B, Martin BM. Proteolytic fragmentation and peptide mapping of human carboxyamidomethylated tracheobronchial mucin. J Biol Chem. 1989 May 15;264(14):8193–8199. [PubMed]
  • Iontcheva I, Oppenheim FG, Troxler RF. Human salivary mucin MG1 selectively forms heterotypic complexes with amylase, proline-rich proteins, statherin, and histatins. J Dent Res. 1997 Mar;76(3):734–743. [PubMed]
  • Sheehan JK, Thornton DJ, Somerville M, Carlstedt I. Mucin structure. The structure and heterogeneity of respiratory mucus glycoproteins. Am Rev Respir Dis. 1991 Sep;144(3 Pt 2):S4–S9. [PubMed]

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