title: Methanobactin and the Link between Copper and Bacterial Methane Oxidation.
abstract: Methanobactins (mbs) are low-molecular-mass (<1,200 Da) copper-binding peptides, or chalkophores, produced by many methane-oxidizing bacteria (methanotrophs). These molecules exhibit similarities to certain iron-binding siderophores but are expressed and secreted in response to copper limitation. Structurally, mbs are characterized by a pair of heterocyclic rings with associated thioamide groups that form the copper coordination site. One of the rings is always an oxazolone and the second ring an oxazolone, an imidazolone, or a pyrazinedione moiety. The mb molecule originates from a peptide precursor that undergoes a series of posttranslational modifications, including (i) ring formation, (ii) cleavage of a leader peptide sequence, and (iii) in some cases, addition of a sulfate group. Functionally, mbs represent the extracellular component of a copper acquisition system. Consistent with this role in copper acquisition, mbs have a high affinity for copper ions. Following binding, mbs rapidly reduce Cu(2+) to Cu(1+). In addition to binding copper, mbs will bind most transition metals and near-transition metals and protect the host methanotroph as well as other bacteria from toxic metals. Several other physiological functions have been assigned to mbs, based primarily on their redox and metal-binding properties. In this review, we examine the current state of knowledge of this novel type of metal-binding peptide. We also explore its potential applications, how mbs may alter the bioavailability of multiple metals, and the many roles mbs may play in the physiology of methanotrophs.
authors.affiliation: Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, USA aland@iastate.edu.
authors.forename: Alan A
authors.initials: AA
authors.lastname: DiSpirito
authors.affiliation: Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Semrau
authors.affiliation: Earth and Life Systems Alliance, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom.
authors.forename: J Colin
authors.initials: JC
authors.lastname: Murrell
authors.affiliation: Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA.
authors.forename: Warren H
authors.initials: WH
authors.lastname: Gallagher
authors.affiliation: Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Christopher
authors.initials: C
authors.lastname: Dennison
authors.affiliation: Department of Microbiology, Genomics and the Environment, UMR 7156 UNISTRA-CNRS, Université de Strasbourg, Strasbourg, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Vuilleumier
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D001665:Binding Sites; D001673:Biodegradation, Environmental; D056831:Coordination Complexes / Q000737:chemistry; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D007093:Imidazoles / Q000737:chemistry; D053858:Metabolic Networks and Pathways; D008697:Methane / Q000378:metabolism; D008772:Methylococcaceae / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000737:chemistry / Q000502:physiology*; D010084:Oxidation-Reduction; D011485:Protein Binding; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D056831:Coordination Complexes; D007093:Imidazoles; D009842:Oligopeptides; D012989:Soil Pollutants; C491147:methanobactin; D003300:Copper; D008697:Methane