Identification of a nonmucin glycoprotein (gp-340) from a purified respiratory mucin preparation: evidence for an association involving the MUC5B mucin.
Rate-zonal centrifugation of a reduced and alkylated respiratory mucin preparation identified a protein-rich fraction. This was subjected to trypsin treatment and one of the many liberated peptides was purified and its N-terminal sequence determined. The peptide was identical to a 14 amino acid sequence from the scavenger receptor cysteine-rich domain containing glycoprotein gp-340. A polyclonal antiserum, raised against the peptide, stained the serous cells in the submucosal glands of human tracheal tissue. The glycoprotein was purified from respiratory mucus by density-gradient centrifugation, gel chromatography, and anion exchange chromatography. The molecule exhibited a heterogeneous distribution of buoyant density (1.28-1.46 g/ml) that overlapped with the gel-forming mucins, was included on Sepharose CL-2B and was quite highly anionic. SDS-PAGE indicated a mass greater than 208 kDa and measurements performed across the molecular size distribution indicated an average M(r) of 5 x 10(5) with a range of M(r) from 2 x 10(5) to 1 x 10(6). Gel chromatography of respiratory mucus extracts ("associative" and "dissociative") indicated that this glycoprotein forms complexes that may involve the large gel-forming mucins MUC5AC and MUC5B. Rate zonal centrifugation suggested such complexes are more likely to involve MUC5B rather than MUC5AC mucins.
Thornton
D J
DJ
Wellcome Trust Centre for Cell-Matrix Research, Division of Biochemistry, School of Biological Sciences, 2.205 Stopford Building, University of Manchester, Manchester, M13 9PT, UK.
Davies
J R
JR
Kirkham
S
S
Gautrey
A
A
Khan
N
N
Richardson
P S
PS
Sheehan
J K
JK
D000595:Amino Acid Sequence; D006801:Humans; D007150:Immunohistochemistry; D046911:Macromolecular Substances; D009005:Monosaccharides / Q000032:analysis; D055257:Mucin-5B; D009077:Mucins / Q000737:chemistry* / Q000302:isolation & purification; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D011971:Receptors, Immunologic / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D014132:Trachea / Q000737:chemistry
C524578:MUC5B protein, human; D046911:Macromolecular Substances; D009005:Monosaccharides; D055257:Mucin-5B; D009077:Mucins; D010446:Peptide Fragments; D011971:Receptors, Immunologic; C116303:glycoprotein 340