title: Unusually high mechanical stability of bacterial adhesin extender domains having calcium clamps.
abstract: To gain insight into the relationship between protein structure and mechanical stability, single molecule force spectroscopy experiments on proteins with diverse structure and topology are needed. Here, we measured the mechanical stability of extender domains of two bacterial adhesins MpAFP and MhLap, in an atomic force microscope. We find that both proteins are remarkably stable to pulling forces between their N- and C- terminal ends. At a pulling speed of 1 μm/s, the MpAFP extender domain fails at an unfolding force Fu = 348 ± 37 pN and MhLap at Fu = 306 ± 51 pN in buffer with 10 mM Ca2+. These forces place both extender domains well above the mechanical stability of many other β-sandwich domains in mechanostable proteins. We propose that the increased stability of MpAFP and MhLap is due to a combination of both hydrogen bonding between parallel terminal strands and intra-molecular coordination of calcium ions.
authors.affiliation: Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands.|Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.
authors.forename: Anneloes S
authors.initials: AS
authors.lastname: Oude Vrielink
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
authors.forename: Tyler D R
authors.initials: TD
authors.lastname: Vance
authors.affiliation: Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands.|Laboratory of Molecular Biosensing for Medical Diagnostics, Department of Applied Physics, Eindhoven University of Technology, Eindhoven, Netherlands.
authors.forename: Arthur M
authors.initials: AM
authors.lastname: de Jong
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Davies
authors.affiliation: Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands.|Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.|Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.
authors.forename: Ilja K
authors.identifier: http://orcid.org/0000-0003-3543-4821
authors.initials: IK
authors.lastname: Voets
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism; D006860:Hydrogen Bonding; D053520:Marinobacter / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D053544:Marinomonas / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D000072417:Protein Domains; D015202:Protein Engineering; D055550:Protein Stability; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D018829:Adhesins, Bacterial; D011994:Recombinant Proteins; D002118:Calcium