Granule-stored MUC5B mucins are packed by the non-covalent formation of N-terminal head-to-head tetramers.

ABSTRACT: Most MUC5B mucin polymers in the upper airways of humans and pigs are produced by submucosal glands. MUC5B forms N-terminal covalent dimers that are further packed into larger assemblies because of low pH and high Ca²⁺ in the secretory granule of the mucin-producing cell. We purified the recombinant MUC5B N-terminal covalent dimer and used single-particle electron microscopy to study its structure under intracellular conditions. We found that, at intragranular pH, the dimeric MUC5B organized into head-to-head noncovalent tetramers where the von Willebrand D1-D2 domains hooked into each other. These N-terminal tetramers further formed long linear complexes from which, we suggest, the mucin domains and their C termini project radially outwards. Using conventional and video microsc

SUBMITTER: Trillo-Muyo S 

PROVIDER: S-EPMC5900763 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature