3RBH

Structure of alginate export protein AlgE from Pseudomonas aeruginosa

Summary for 3RBH

• Entry DOI: 10.2210/pdb3rbh/pdb
• Descriptor: Alginate production protein AlgE, CALCIUM ION, 1,2-ETHANEDIOL, ... (5 entities in total)
• Functional Keywords: beta-barrel, alginate export, membrane protein, transport protein
• Biological source: Pseudomonas aeruginosa
• Cellular location: Cell outer membrane; Peripheral membrane protein: P18895
• Total number of polymer chains: 4
• Total formula weight: 225670.41

Authors

Whitney, J.C.,Hay, I.D.,Li, C.,Eckford, P.D.,Robinson, H.,Amaya, M.F.,Wood, L.F.,Ohman, D.E.,Bear, C.E.,Rehm, B.H.,Howell, P.L. (deposition date: 2011-03-29, release date: 2011-07-27, Last modification date: 2024-10-16)

Primary citation

Whitney, J.C.,Hay, I.D.,Li, C.,Eckford, P.D.,Robinson, H.,Amaya, M.F.,Wood, L.F.,Ohman, D.E.,Bear, C.E.,Rehm, B.H.,Lynne Howell, P.
Structural basis for alginate secretion across the bacterial outer membrane.
Proc.Natl.Acad.Sci.USA, 108:13083-13088, 2011

PubMed Abstract: Pseudomonas aeruginosa is the predominant pathogen associated with chronic lung infection among cystic fibrosis patients. During colonization of the lung, P. aeruginosa converts to a mucoid phenotype characterized by the overproduction of the exopolysaccharide alginate. Secretion of newly synthesized alginate across the outer membrane is believed to occur through the outer membrane protein AlgE. Here we report the 2.3 Å crystal structure of AlgE, which reveals a monomeric 18-stranded β-barrel characterized by a highly electropositive pore constriction formed by an arginine-rich conduit that likely acts as a selectivity filter for the negatively charged alginate polymer. Interestingly, the pore constriction is occluded on either side by extracellular loop L2 and an unusually long periplasmic loop, T8. In halide efflux assays, deletion of loop T8 (ΔT8-AlgE) resulted in a threefold increase in anion flux compared to the wild-type or ΔL2-AlgE supporting the idea that AlgE forms a transport pathway through the membrane and suggesting that transport is regulated by T8. This model is further supported by in vivo experiments showing that complementation of an algE deletion mutant with ΔT8-AlgE impairs alginate production. Taken together, these studies support a mechanism for exopolysaccharide export across the outer membrane that is distinct from the Wza-mediated translocation observed in canonical capsular polysaccharide export systems.

PubMed: 21778407
DOI: 10.1073/pnas.1104984108

Experimental method

X-RAY DIFFRACTION (2.301 Å)