title: Structural and functional characterization of a recombinant PorB class 2 protein from Neisseria meningitidis. Conformational stability and porin activity.
abstract: An outer membrane PorB class 2 protein from Neisseria meningitidis has been overexpressed in Escherichia coli, isolated from inclusion bodies, and refolded in the presence of zwitterionic detergent. The purified recombinant and native (strain M986) counterpart exhibit most of the typical functional and structural properties that are characteristic of bacterial porins. Channel forming activity has been monitored by incorporating class 2 into reconstituted liposomes and measuring the permeation rates of various oligosaccharides through the proteoliposomes to derive a pore diameter of approximately 1.6 nm. Structural studies employing a combination of spectroscopic and electrophoretic techniques reveal that recombinant and native class 2 are identical in terms of overall conformational stability. Both proteins form stable trimers in zwitterionic detergent and retain significant secondary and tertiary structure in the presence of SDS. The thermal unfolding of zwittergen-solubilized class 2 trimers (Tm = 88 degrees C) is reversible and characterized by solvent exposure of aromatic residues with concomitant disruption of tertiary and partial loss of secondary structures. SDS-induced destabilization and irreversible unfolding of the native trimeric assembly occurs at temperatures above 60 degrees C. Our physicochemical studies of PorB class 2 protein furnish significant insight regarding the structural and functional properties of this meningococcal outer membrane protein within the porin superfamily.
authors.affiliation: North American Vaccine, Inc., Beltsville, Maryland 20705, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Minetti
authors.forename: J Y
authors.initials: JY
authors.lastname: Tai
authors.forename: M S
authors.initials: MS
authors.lastname: Blake
authors.forename: J K
authors.initials: JK
authors.lastname: Pullen
authors.forename: S M
authors.initials: SM
authors.lastname: Liang
authors.forename: D P
authors.initials: DP
authors.lastname: Remeta
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D019791:Guanidine; D006146:Guanidines; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009345:Neisseria meningitidis / Q000378:metabolism*; D018272:Porins; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D012967:Sodium Dodecyl Sulfate; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D006146:Guanidines; D046911:Macromolecular Substances; D018272:Porins; D011994:Recombinant Proteins; C057699:porin protein, Neisseria; D012967:Sodium Dodecyl Sulfate; D019791:Guanidine