The outer membranes of Gram-negative bacteria are naturally insulative and prevent the indiscriminate exchange of electrons between the cell and environment. However, a number of important bacterial processes require the conductance of electrons across the outer membrane. These include the transfer of intracellularly derived electrons out of the cell to external electron acceptors or the import of electrons into the cell from extracellular electron donors in order to support the formation of reducing equivalents for carbon fixation. The ability to directly transfer electrons into and out of bacterial cells is also of increasing interest for biotechnological applications including microbial fuel cells, microbial electrosynthesis, unbalanced fermentation, and bio-electronic interfaces. The Gram-negative Shewanella is one of the most studied bacterial genera capable of transferring electrons out of the cell to solid-phase Fe(III) and Mn(IV) minerals in order to support anaerobic respiration. The ternary Mltr complex (MtrA, MtrB, MtrC) from the outer membrane of Shewanella oneidensis is able to conduct electrons bidirectionally across proteoliposome bilayers sustaining electron transport rates over 8,500 e s–1. MtrAB is proposed to span the outer membrane and provide electrical connection between the catabolic electron transfer network within the cell, and the electron dispersing MtrC outside the cell. This is one of the most amazing protein structures solved in the last years, showing how a transmission microcable is insulated to span across membranes. Here you can see the X-ray structure of this biological insulated transmembrane molecular wire from Shewanella baltica (PDB code: 6R2Q)

#scivis #molecularart #shewanella #cable #insulator #membrane #conductivity #xray

Structure rendered with @proteinimaging, post-processed with @stylar.ai_official and depicted with @corelphotopaint