Structural studies of the Cpx pathway activator NlpE on the outer membrane of Escherichia coli.
NlpE, an outer membrane lipoprotein, functions during envelope stress responses in Gram-negative bacteria. In Escherichia coli, adhesion to abiotic surfaces has been reported to activate the Cpx pathway in an NlpE-dependent manner. External copper ions are also thought to activate the Cpx pathway mediated by NlpE. We determined the crystal structure of NlpE from E. coli at 2.6 A resolution. The structure showed that NlpE consists of two beta barrel domains. The N-terminal domain resembles the bacterial lipocalin Blc, and the C-terminal domain has an oligonucleotide/oligosaccharide-binding (OB) fold. From both biochemical analyses and the crystal structure, it can be deduced that the cysteine residues in the CXXC motif may be chemically active. Furthermore, two monomers in the asymmetric unit form an unusual 3D domain-swapped dimer. These findings indicate that tertiary and/or quaternary structural instability may be responsible for Cpx pathway activation.
Hirano
Yu
Y
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Hossain
Md Motarab
MM
Takeda
Kazuki
K
Tokuda
Hajime
H
Miki
Kunio
K
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013059:Spectrum Analysis, Raman
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C110674:CpxP protein, bacteria; D004220:Disulfides; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D008565:Membrane Proteins