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BMC Biology

, 11:17

First Online: 26 February 2013Received: 21 December 2012Accepted: 26 February 2013DOI: 10.1186-1741-7007-11-17

Cite this article as: Kenney, G.E. & Rosenzweig, A.C. BMC Biol 2013 11: 17. doi:10.1186-1741-7007-11-17


BackgroundMethanobactins Mbns are a family of copper-binding natural products involved in copper uptake by methanotrophic bacteria. The few Mbns that have been structurally characterized feature copper coordination by two nitrogen-containing heterocycles next to thioamide groups embedded in a peptidic backbone of varying composition. Mbns are proposed to derive from post-translational modification of ribosomally synthesized peptides, but only a few genes encoding potential precursor peptides have been identified. Moreover, the relevance of neighboring genes in these genomes has been unclear.

ResultsThe potential for Mbn production in a wider range of bacterial species was assessed by mining microbial genomes. Operons encoding Mbn-like precursor peptides, MbnAs, were identified in 16 new species, including both methanotrophs and, surprisingly, non-methanotrophs. Along with MbnA, the core of the operon is formed by two putative biosynthetic genes denoted MbnB and MbnC. The species can be divided into five groups on the basis of their MbnA and MbnB sequences and their operon compositions. Additional biosynthetic proteins, including aminotransferases, sulfotransferases and flavin adenine dinucleotide FAD-dependent oxidoreductases were also identified in some families. Beyond biosynthetic machinery, a conserved set of transporters was identified, including MATE multidrug exporters and TonB-dependent transporters. Additional proteins of interest include a di-heme cytochrome c peroxidase and a partner protein, the roles of which remain a mystery.

ConclusionsThis study indicates that Mbn-like compounds may be more widespread than previously thought, but are not present in all methanotrophs. This distribution of species suggests a broader role in metal homeostasis. These data provide a link between precursor peptide sequence and Mbn structure, facilitating predictions of new Mbn structures and supporting a post-translational modification biosynthetic pathway. In addition, testable models for Mbn transport and for methanotrophic copper regulation have emerged. Given the unusual modifications observed in Mbns characterized thus far, understanding the roles of the putative biosynthetic proteins is likely to reveal novel pathways and chemistry.

Keywordsmethanobactin methanotroph particulate methane monooxygenase copper chalkophore TonB-dependent transporter natural product post-translational modification AbbreviationsAaamino acids

ABCATP-binding cassette

ATPadenosine triphosphate

BLASTBasic Local Alignment Search Tool

ECFextracytoplasmic function

FADflavin adenine dinucleotide

HMMhidden Markov model

MATEmultidrug and toxic compound extrusion


MFSmajor facilitator superfamily

MMOmethane monooxygenase

Mrnamessenger ribonucleic acid

NExTN-terminal extension

NMRnuclear magnetic resonance

ORFopen reading frame

pMMOparticulate methane monooxygenase

RiPPribosomally synthesized and post-translationally modified peptide natural product

RNDresistance-nodulation-cell division

SACCPsurface-associated cytochrome c peroxidase

SAMS-adenosyl methionine

sMMOsoluble methane monooxygenase

TBDTtonB-dependent transporter.

Electronic supplementary materialThe online version of this article doi:10.1186-1741-7007-11-17 contains supplementary material, which is available to authorized users.

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Autor: Grace E Kenney - Amy C Rosenzweig


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