Chemistry and Biology of the Copper Chelator Methanobactin

Abstract

Methanotrophic bacteria, organisms that oxidize methane, produce a small copper chelating molecule called methanobactin (Mb). Mb binds Cu(I) with high affinity and is hypothesized to mediate copper acquisition from the environment. Recent advances in Mb characterization include revision of the chemical structure of Mb from Methylosinus trichosporium OB3b and further investigation of its biophysical properties. In addition, Mb production by several other methanotroph strains has been investigated and preliminary characterization suggests diversity in chemical composition. Initial clues into Mb biosynthesis have been obtained by identification of a putative precursor gene in the M. trichosporium OB3b genome. Finally, direct uptake of intact Mb into the cytoplasm of M. trichosporium OB3b cells has been demonstrated and studies of the transport mechanism have been initiated. Taken together, these advances represent significant progress and set the stage for exciting new research directions.

Magnetic susceptibility of Mn(III) complexes of hydroxamate siderophores

“…While ligand-mediated uptake of metals other than iron has been demonstrated recently for molybdenum and vanadium with siderophores [3,34] and for copper with chalkophores [35,36], ligand-mediated uptake of manganese has not been reported to date. Nevertheless, siderophores may play an important role in biogenic cycling of manganese [10,19,37,38] .…”

Metallophores and Trace Metal Biogeochemistry

“…Methanotrophs oxidize methane by a soluble or a membrane-bound particulate form of methane monooxygenase enzyme (MMO). Under copper replete conditions, high intracellular concentrations of the copper-containing particulate methane monooxygenase (pMMO) are found in methanotrophic bacterial species (Kenney and Rosenzweig 2012). Some methanotrophs react to Cu limitation by expressing soluble MMO (sMMO) containing a di-iron center.…”

Bacterial Copper Resistance and Virulence

“…Outer membrane channels such as OmpF and the E. coli ComC [20], metal permeases bound to the cell membrane such as ZupT from E. coli [21], or even broad substrate range ABC-transporters such as MstABC from Streptococcus pyogenes [22], and ATPases such as HmtA from P. aeruginosa [23], were also found to mediate Cu acquisition. Some species were reported to secrete chelators such as copper-specific methanobactin and coproporphyrin or Feuptake siderophores that are essential to acquire the metal from the medium under Cu-limiting conditions [24]. In some cases they can also sequester the metal outside the cell to avoid toxicity.…”