Methanotrophic bacteria catalyze the activation of methane using enzymes which incorporate Cu and excrete small peptides known as methanobactins for extracellular copper acquisition. In addition to Cu, these peptides interact strongly with other late transition metals including Zn, Cd, and Hg, and represent a nexus between the biogeochemistry of methane and the biogeochemical cycles of the late transition metals. We combine spectroscopic, computational, and thermodynamic data to characterize the complexation of Group 11 and 12 transition metals by methanobactins excreted by <i>methylocystis sp.</i> strain SB2. We propose a mechanism for a fluorescence enhancement observed complexes of mb-SB2 with specific transition metals and use the near-UV absorbance of the peptide to study competition between the methanobactins and specific organic compounds chosen as models for dissolved organic matter for complexation of Group 12 transition metals. We find that methanobactins are generally strong chelating agents for late transition metals but that out-competition of the peptide may occur in the presence of specific ligand types. Our data represents the first computational investigation of the peptides of which we are aware and creates a baseline for further study of the peptides and the intermolecular interactions which may modulate their function in extracellular copper acquisition.

Spectroscopic and thermodynamic signatures of organometallic complexation and ligand competition in methanobactin chalkophores

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.