Structure of the Neisserial Outer Membrane Protein Opa₆₀: Loop Flexibility Essential to Receptor Recognition and Bacterial Engulfment

Abstract

The structure and dynamics of Opa proteins, which we report herein, are responsible for the receptor-mediated engulfment of Neisseria gonorrheae or Neisseria meningitidis by human cells and can offer deep understanding into the molecular recognition of pathogen–host receptor interactions. Such interactions are vital to understanding bacterial pathogenesis as well as the mechanism of foreign body entry to a human cell, which may provide insights for the development of targeted pharmaceutical delivery systems. The size and dynamics of the extracellular loops of Opa60 required a hybrid refinement approach wherein membrane and distance restraints were used to generate an initial NMR structural ensemble, which was then further refined using molecular dynamics in a DMPC bilayer. The resulting ensemble revealed that the extracellular loops, which bind host receptors, occupy compact conformations, interact with each other weakly, and are dynamic on the nanosecond time scale. We predict that this conformational sampling is critical for enabling diverse Opa loop sequences to engage a common set of receptors.

Lipid Internal Dynamics Probed in Nanodiscs

“…A comparison of membrane protein dynamics in micelles and nanodiscs revealed that micelles compromised the inherent flexibility of the protein, despite conservation of the structure 21, 28. Recent investigations into membrane proteins4, 19, 22, 25 have revealed that nanodiscs are a suitable tool to reconstitute membrane proteins in a native environment to solve their three‐dimensional structure with atomic resolution. They are derived from apolipoprotein A1 (ApoA‐1), which solubilises hydrophobic molecules, such as lipids and cholesterol, to deliver them to the liver through the blood and interstitial fluid as high‐density lipoprotein (HDL) particles 16, 27.…”

Influence of the lipid membrane environment on structure and activity of the outer membrane protein Ail from Yersinia pestis

“…Solid-state NMR methods can be used for proteins in a variety of lipid bilayer assemblies, including planar supported lipid bilayers, lipid bilayer macrodiscs and liposomes [4–10]. More recently, lipid bilayer nanodiscs [11, 12] have been used effectively for solution NMR studies of membrane proteins [13–24]. …”

Cover Feature: Lipid Internal Dynamics Probed in Nanodiscs (ChemPhysChem 19/2017)

“…[11,36] Ac omparison of membrane protein dynamics in micellesa nd nanodiscs revealed that micelles compromised the inherentf lexibility of the protein, despite conservation of the structure. [21,28] Recent investigations into membrane proteins [4,19,22,25] have revealed that nanodiscs are as uitable tool to reconstitute membrane proteins in an ative environmentt o solve their three-dimensional structure with atomic resolution. They are derived from apolipoprotein A1 (ApoA-1), whichs olubilisesh ydrophobic molecules,s uch as lipids and cholesterol, Nanodiscs offer av ery promising tool to incorporate membrane proteins into native-like lipid bilayers and an alternative to liposomest om aintain protein functions and protein-lipid interactions in as oluble nanoscale object.…”