Format

Send to

Choose Destination
FEBS J. 2018 May;285(10):1812-1826. doi: 10.1111/febs.14441. Epub 2018 Apr 6.

Conserved structural features anchor biofilm-associated RTX-adhesins to the outer membrane of bacteria.

Author information

1
Protein Function Discovery Group, Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada.
2
Institute for Complex Molecular Systems, Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, the Netherlands.
3
Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, the Netherlands.

Abstract

Repeats-in-toxin (RTX) adhesins are present in many Gram-negative bacteria to facilitate biofilm formation. Previously, we reported that the 1.5-MDa RTX adhesin (MpIBP) from the Antarctic bacterium, Marinomonas primoryensis, is tethered to the bacterial cell surface via its N-terminal Region I (RI). Here, we show the detailed structural features of RI. It has an N-terminal periplasmic retention domain (RIN), a central domain (RIM) that can insert into the β-barrel of an outer-membrane pore protein during MpIBP secretion, and three extracellular domains at its C terminus (RIC) that transition the protein into the extender region (RII). RIN has a novel β-sandwich fold with a similar shape to βγ-crystallins and tryptophan RNA attenuation proteins. Because RIM undergoes fast and extensive degradation in vitro, its narrow cylindrical shape was rapidly measured by small-angle X-ray scattering before proteolysis could occur. The crystal structure of RIC comprises three tandem β-sandwich domains similar to those in RII, but increasing in their hydrophobicity with proximity to the outer membrane. In addition, the key Ca2+ ion that rigidifies the linkers between RII domains is not present between the first two of these RIC domains. This more flexible RI linker near the cell surface can act as a 'pivot' to help the 0.6-μm-long MpIBP sweep over larger volumes to find its binding partners. Since the physical features of RI are well conserved in the RTX adhesins of many Gram-negative bacteria, our detailed structural and bioinformatic analyses serve as a model for investigating the surface retention of biofilm-forming bacteria, including human pathogens.

KEYWORDS:

bacterial adhesins; biofilms; structural biology; surface-retention domains

PMID:
29575515
DOI:
10.1111/febs.14441
[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center