4B61

In meso structure of alginate transporter, AlgE, from Pseudomoas aeruginosa, PAO1. Crystal form 3.

Summary for 4B61

• Entry DOI: 10.2210/pdb4b61/pdb
• Related: 4AFK 4AZL
• Descriptor: ALGINATE PRODUCTION PROTEIN ALGE, (2S)-2,3-DIHYDROXYPROPYL(7Z)-PENTADEC-7-ENOATE, LAURYL DIMETHYLAMINE-N-OXIDE, ... (8 entities in total)
• Functional Keywords: membrane protein, outer membrane, in meso crystallisation, lipidic cubic phase
• Biological source: PSEUDOMONAS AERUGINOSA PAO1
• Total number of polymer chains: 2
• Total formula weight: 110513.01

Authors

Tan, J.,Pye, V.E.,Aragao, D.,Caffrey, M. (deposition date: 2012-08-08, release date: 2013-07-17, Last modification date: 2024-02-07)

Primary citation

Tan, J.,Rouse, S.L.,Li, D.,Pye, V.E.,Vogeley, L.,Brinth, A.R.,El Arnaout, T.,Whitney, J.C.,Howell, P.L.,Sansom, M.S.P.,Caffrey, M.
A Conformational Landscape for Alginate Secretion Across the Outer Membrane of Pseudomonas Aeruginosa.
Acta Crystallogr.,Sect.D, 70:2054-, 2014

PubMed Abstract: The exopolysaccharide alginate is an important component of biofilms produced by Pseudomonas aeruginosa, a major pathogen that contributes to the demise of cystic fibrosis patients. Alginate exits the cell via the outer membrane porin AlgE. X-ray structures of several AlgE crystal forms are reported here. Whilst all share a common β-barrel constitution, they differ in the degree to which loops L2 and T8 are ordered. L2 and T8 have been identified as an extracellular gate (E-gate) and a periplasmic gate (P-gate), respectively, that reside on either side of an alginate-selectivity pore located midway through AlgE. Passage of alginate across the membrane is proposed to be regulated by the sequential opening and closing of the two gates. In one crystal form, the selectivity pore contains a bound citrate. Because citrate mimics the uronate monomers of alginate, its location is taken to highlight a route through AlgE taken by alginate as it crosses the pore. Docking and molecular-dynamics simulations support and extend the proposed transport mechanism. Specifically, the P-gate and E-gate are flexible and move between open and closed states. Citrate can leave the selectivity pore bidirectionally. Alginate docks stably in a linear conformation through the open pore. To translate across the pore, a force is required that presumably is provided by the alginate-synthesis machinery. Accessing the open pore is facilitated by complex formation between AlgE and the periplasmic protein AlgK. Alginate can thread through a continuous pore in the complex, suggesting that AlgK pre-orients newly synthesized exopolysaccharide for delivery to AlgE.

PubMed: 25084326
DOI: 10.1107/S1399004714001850

Experimental method

X-RAY DIFFRACTION (2.402 Å)