Manganese biomineralization by the bacterial protein complex Mnx
EMSL Project ID
50773
Abstract
Manganese-oxide mineral formation by bacterial oxidation of dissolved Mn(II) is an important process in aquatic and soil environments and is a key part of the global Mn cycle. The Mn bio-oxides represent highly reactive phases that sorb metal ions and oxidize numerous organic and inorganic species, driving the biogeochemical cycling of nutrients and contaminants. In many phylogenetically diverse model systems for Mn(II)-oxidizing bacteria, multicopper oxidase enzymes have been implicated to be the catalysts for Mn(II) oxidation. These enzymes reside in exosporium -- a complex structure of carbohydrates and proteins that surrounds the spore coats of some bacterial spores. The Tebo lab has recently succeeded in producing active Mn oxidase from Bacillus sp. PL-12 in E. coli by co-expressing three out of the four genes in the polycistronic mnx operon. The enzyme, which we call Mnx, is the first purified manganese oxidase, and it is solely responsible for both Mn oxidation and MnO2 mineral formation. Present knowledge of manganese biomineralization provides only a provisional view of how the enzyme forms the biomineral. The objective of this interdisciplinary project is to develop a comprehensive picture of bacterial manganese biomineralization, determining the mechanism of MnO2 formation by manganese oxidase Mnx, and how this mechanism is modified by bacterial cell components.To understand manganese mineralization with molecular-level details, our proposed research approach focuses on three overarching questions:
1. What are the atomic-level structure of Mn oxidase protein and the nature of the mineral product-protein interactions?
2. What are primary particles exiting the protein? What is their assembly mechanism to form layered-structure Mn(IV) oxide mineral?
3. How do the biological components of the living cells modify the MnO2 mineralization process?
The project is highly leveraged through an integrated approach of multiple state-of-the-art capabilities at EMSL (cryo-EM, liquid-cell TEM, and native mass spectroscopy) to increase our understanding of the biomineralization mechanism by visualizing the formation of MnO2 minerals on the protein, and the whole cell. This new information, coupled with the previously developed knowledge of Mn oxide structure and chemistry could lead to the development of bio-oxide materials optimized for practical applications in environmental remediation and bioenergy production.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2019-10-01
End Date
2022-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members