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PLoS One. 2017 Apr 4;12(4):e0174682. doi: 10.1371/journal.pone.0174682. eCollection 2017.

Unusually high mechanical stability of bacterial adhesin extender domains having calcium clamps.

Author information

1
Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, Netherlands.
2
Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.
3
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
4
Laboratory of Molecular Biosensing for Medical Diagnostics, Department of Applied Physics, Eindhoven University of Technology, Eindhoven, Netherlands.
5
Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.

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.

PMID:
28376122
PMCID:
PMC5380327
DOI:
10.1371/journal.pone.0174682
[Indexed for MEDLINE]
Free PMC Article

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