Methanobactin transport machinery.
Methanotrophic bacteria use methane, a potent greenhouse gas, as their primary source of carbon and energy. The first step in methane metabolism is its oxidation to methanol. In almost all methanotrophs, this chemically challenging reaction is catalyzed by particulate methane monooxygenase (pMMO), a copper-dependent integral membrane enzyme. Methanotrophs acquire copper (Cu) for pMMO by secreting a small ribosomally produced, posttranslationally modified natural product called methanobactin (Mbn). Mbn chelates Cu with high affinity, and the Cu-loaded form (CuMbn) is reinternalized into the cell via an active transport process. Bioinformatic and gene regulation studies suggest that two proteins might play a role in CuMbn handling: the TonB-dependent transporter MbnT and the periplasmic binding protein MbnE. Disruption of the gene that encodes MbnT abolishes CuMbn uptake, as reported previously, and expression of MbnT in Escherichia coli confers the ability to take up CuMbn. Biophysical studies of MbnT and MbnE reveal specific interactions with CuMbn, and a crystal structure of apo MbnE is consistent with MbnE's proposed role as a periplasmic CuMbn transporter. Notably, MbnT and MbnE exhibit different levels of discrimination between cognate and noncognate CuMbns. These findings provide evidence for CuMbn-protein interactions and begin to elucidate the molecular mechanisms of its recognition and transport.
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208.
Laura M K
LM
Dassama
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208.
Grace E
GE
Kenney
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208.
Soo Y
SY
Ro
Department of Chemistry, Northwestern University, Evanston, IL 60208.
Eliza L
EL
Zielazinski
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208; amyr@northwestern.edu.|Department of Chemistry, Northwestern University, Evanston, IL 60208.
Amy C
0000-0001-8472-4134
AC
Rosenzweig
D001688:Biological Products / Q000378:metabolism; D001692:Biological Transport; D003300:Copper / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D007093:Imidazoles / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism; D033902:Periplasmic Binding Proteins / Q000378:metabolism
D001688:Biological Products; D029968:Escherichia coli Proteins; D007093:Imidazoles; D008565:Membrane Proteins; D009842:Oligopeptides; D033902:Periplasmic Binding Proteins; C491147:methanobactin; C489181:tonB protein, E coli; D003300:Copper; D010105:Oxygenases; C021555:methane monooxygenase
chalkophore; copper transport; metal homeostasis; methane monooxygenase; methanobactin