Lipid Headgroup Charge and Acyl Chain Composition Modulate Closure of Bacterial β-Barrel Channels. 2019

D Aurora Perini, and Antonio Alcaraz, and María Queralt-Martín
Laboratory of Molecular Biophysics, Department of Physics, Universitat Jaume I, 12071 Castellón, Spain. perini@uji.es.

The outer membrane of Gram-negative bacteria contains β-barrel proteins that form high-conducting ion channels providing a path for hydrophilic molecules, including antibiotics. Traditionally, these proteins have been considered to exist only in an open state so that regulation of outer membrane permeability was accomplished via protein expression. However, electrophysiological recordings show that β-barrel channels respond to transmembrane voltages by characteristically switching from a high-conducting, open state, to a so-called 'closed' state, with reduced permeability and possibly exclusion of large metabolites. Here, we use the bacterial porin OmpF from E. coli as a model system to gain insight on the control of outer membrane permeability by bacterial porins through the modulation of their open state. Using planar bilayer electrophysiology, we perform an extensive study of the role of membrane lipids in the OmpF channel closure by voltage. We pay attention not only to the effects of charges in the hydrophilic lipid heads but also to the contribution of the hydrophobic tails in the lipid-protein interactions. Our results show that gating kinetics is governed by lipid characteristics so that each stage of a sequential closure is different from the previous one, probably because of intra- or intermonomeric rearrangements.

UI MeSH Term Description Entries
D008051 Lipid Bilayers Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes. Bilayers, Lipid,Bilayer, Lipid,Lipid Bilayer
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D010743 Phospholipids Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system. Phosphatides,Phospholipid
D000072757 Protein Conformation, beta-Strand A secondary structure of proteins where the amino (N-H) groups of a polypeptide backbone, three to ten amino acids in length, establish hydrogen bonds with the carbonyl (C Protein Conformation, beta-Sheet,beta-Pleated Sheet,beta-Sheet,beta-Sheets,beta-Strand,beta-Stranded Structures,beta-Strands,Conformation, beta-Sheet Protein,Conformation, beta-Strand Protein,Conformations, beta-Sheet Protein,Conformations, beta-Strand Protein,Protein Conformation, beta Sheet,Protein Conformation, beta Strand,Protein Conformations, beta-Sheet,Protein Conformations, beta-Strand,Sheet, beta-Pleated,Sheets, beta-Pleated,beta Pleated Sheet,beta Sheet,beta Sheets,beta Strand,beta Stranded Structures,beta Strands,beta-Pleated Sheets,beta-Sheet Protein Conformation,beta-Sheet Protein Conformations,beta-Strand Protein Conformation,beta-Strand Protein Conformations,beta-Stranded Structure
D000215 Acylation The addition of an organic acid radical into a molecule.
D015640 Ion Channel Gating The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability. Gating, Ion Channel,Gatings, Ion Channel,Ion Channel Gatings
D048168 Escherichia coli K12 A species of gram-negative, rod-shaped bacteria belonging to the K serogroup of ESCHERICHIA COLI. It lives as a harmless inhabitant of the human LARGE INTESTINE and is widely used in medical and GENETIC RESEARCH. E coli K12
D055503 Protein Multimerization The assembly of the QUATERNARY PROTEIN STRUCTURE of multimeric proteins (MULTIPROTEIN COMPLEXES) from their composite PROTEIN SUBUNITS. Protein Dimerization,Protein Heteromultimerizaton,Protein Multimer Assembly,Protein Trimerization,Assembly, Protein Multimer,Dimerization, Protein,Heteromultimerizaton, Protein,Heteromultimerizatons, Protein,Multimer Assembly, Protein,Multimerization, Protein,Trimerization, Protein
D057927 Hydrophobic and Hydrophilic Interactions The thermodynamic interaction between a substance and WATER. Hydrophilic Interactions,Hydrophilic and Hydrophobic Interactions,Hydrophilicity,Hydrophobic Interactions,Hydrophobicity,Hydrophilic Interaction,Hydrophilicities,Hydrophobic Interaction,Hydrophobicities,Interaction, Hydrophilic,Interaction, Hydrophobic,Interactions, Hydrophilic,Interactions, Hydrophobic
D018272 Porins Porins are protein molecules that were originally found in the outer membrane of GRAM-NEGATIVE BACTERIA and that form multi-meric channels for the passive DIFFUSION of WATER; IONS; or other small molecules. Porins are present in bacterial CELL WALLS, as well as in plant, fungal, mammalian and other vertebrate CELL MEMBRANES and MITOCHONDRIAL MEMBRANES. Pore Protein,Pore Proteins,Porin,Protein, Pore,Proteins, Pore

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