Molecular mapping of statherin- and histatin-binding domains in human salivary mucin MG1 (MUC5B) by the yeast two-hybrid system.
MGI is a high-molecular-weight mucin secreted by mucous acinar cells in human submandibular and sublingual glands. We have recently shown that the tracheobronchial mucin MUC5B is a major component of MG1. MUC5B is organized into cysteine-rich N- and C-terminal regions that flank a central tandem-repeat region containing cysteine-rich subdomains and imperfect 29-residue tandem repeats. In earlier work, we have shown that this mucin selectively forms heterotypic complexes with amylase, proline-rich proteins, statherin, and histatins in salivary secretions, and the aim of this study was to identify specific binding domains within MUC5B using the yeast two-hybrid system. Interactions of cysteine-rich domains in the tandem-repeat region (Cys1-Cys4) and C-terminal region (Cys8a, Cys8b, Cys8c) of MUC5B with statherin and histatins were investigated. These studies indicated that histatin 1 selectively bound to Cysl and Cys2, whereas statherin and histatin 1, 3, and 5 selectively bound to Cys8a. Analysis of the primary sequences of the identified binding domains suggests that these domains most probably can fold into globular-like structures in the native mucin. A ProDom blast search revealed that sequences in Cys1, Cys2, and Cys8a exhibit similarity to domains in evolutionarily diverse extracellular proteins known to participate in a wide variety of protein-protein interactions.
Iontcheva
I
I
Department of Biochemistry, Boston University School of Medicine, MA 02118, USA.
Oppenheim
F G
FG
Offner
G D
GD
Troxler
R F
RF
D000681:Amylases / Q000737:chemistry; D015153:Blotting, Western; D001980:Bronchi / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics*; D006639:Histidine / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D008970:Molecular Weight; D055257:Mucin-5B; D009077:Mucins / Q000737:chemistry / Q000235:genetics*; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D055232:Proline-Rich Protein Domains; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000235:genetics*; D013361:Sublingual Gland / Q000378:metabolism; D013363:Submandibular Gland / Q000378:metabolism; D020080:Tandem Repeat Sequences / Q000235:genetics; D014132:Trachea / Q000378:metabolism; D015003:Yeasts / Q000235:genetics; D000099053:Histidine-Rich Glycoprotein
D006023:Glycoproteins; C524578:MUC5B protein, human; D055257:Mucin-5B; D009077:Mucins; D010455:Peptides; D010750:Phosphoproteins; D011506:Proteins; C018149:STATH protein, human; D012471:Salivary Proteins and Peptides; D000099053:Histidine-Rich Glycoprotein; D006639:Histidine; D011392:Proline; D000681:Amylases; D003545:Cysteine