Insight into Metal Removal from Peptides that Sequester Copper for Methane Oxidation

Methanobactins (Mbns) are modified peptides that sequester copper (Cu) methanotrophs use to oxidize methane. Limited structural information is available for this class of natural products, as is an understanding of how cells are able to utilize Mbn-bound Cu. The crystal structure of Methylosinus sporium NR3K Cu-I-Mbn provides further information about the structural diversity of Mbns and the first insight into their Cu-release mechanism. Nitrogen ligands from oxazolone and pyrazinediol rings chelate Cu-I along with adjacent coordinating sulfurs from thioamides. In vitro solution data are consistent with a Cu-I-Mbn monomer as found for previously characterized Mbns. In the crystal structure, the N-terminal region has undergone a conformational change allowing the formation of a Cu-2(I)-Mbn(2) dimer with Cu-I sites bound by chelating units from adjacent chains. Such a structural alteration will facilitate Cu-I release from Mbns.