title: Unfolding dynamics of the mucin SEA domain probed by force spectroscopy suggest that it acts as a cell-protective device.
abstract: MUC1 and other membrane-associated mucins harbor long, up to 1 μm, extended highly glycosylated mucin domains and sea urchin sperm protein, enterokinase and agrin (SEA) domains situated on their extracellular parts. These mucins line luminal tracts and organs, and are anchored to the apical cell membrane by a transmembrane domain. The SEA domain is highly conserved and undergoes a molecular strain-dependent autocatalytic cleavage during folding in the endoplasmic reticulum, a process required for apical plasma membrane expression. To date, no specific function has been designated for the SEA domain. Here, we constructed a recombinant protein consisting of three SEA domains in tandem and used force spectroscopy to assess the dissociation force required to unfold individual, folded SEA domains. Force-distance curves revealed three peaks, each representing unfolding of a single SEA domain. Fitting the observed unfolding events to a worm-like chain model yielded an average contour length of 32 nm per SEA domain. Analysis of forces applied on the recombinant protein revealed an average unfolding force of 168 pN for each SEA domain at a loading rate of 25 nN·s(-1). Thus, the SEA domain may act as a breaking point that can dissociate before the plasma membrane is breached when mechanical forces are applied to cell surfaces.
authors: Department of Medical Biochemistry, University of Gothenburg, Gothenburg, Sweden.
authors: Thaher
authors: T
authors: Pelaseyed
authors: Michael
authors: M
authors: Zäch
authors: Asa C
authors: AC
authors: Petersson
authors: Frida
authors: F
authors: Svensson
authors: Denny G A
authors: DG
authors: Johansson
authors: Gunnar C
authors: GC
authors: Hansson
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D016466:CHO Cells; D002462:Cell Membrane / Q000737:chemistry; D006224:Cricetinae; D004797:Enzyme-Linked Immunosorbent Assay; D018625:Microscopy, Atomic Force / Q000379:methods*; D008958:Models, Molecular; D018396:Mucin-1 / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D059748:Proteolysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013314:Stress, Mechanical; D013696:Temperature; D014162:Transfection
chemical_list: D018396:Mucin-1; D011994:Recombinant Proteins