Cryo-EM structures of engineered active bc₁-cbb₃ type CIII₂CIV super-complexes and electronic communication between the complexes.

ABSTRACT: Respiratory electron transport complexes are organized as individual entities or combined as large supercomplexes (SC). Gram-negative bacteria deploy a mitochondrial-like cytochrome (cyt) bc₁ (Complex III, CIII₂), and may have specific cbb₃-type cyt c oxidases (Complex IV, CIV) instead of the canonical aa₃-type CIV. Electron transfer between these complexes is mediated by soluble (c₂) and membrane-anchored (c_y) cyts. Here, we report the structure of an engineered bc₁-cbb₃ type SC (CIII₂CIV, 5.2?Å resolution) and three conformers of native CIII₂ (3.3?Å resolution). The SC is active in vivo and in vitro, contains all catalytic subunits and cofactors, and two extra transmembrane helices attributed to cyt c_y and the assembly factor CcoH. The cyt c_y is integral to SC, its cyt domain is mobile and it conveys electrons to CIV differently than cyt c₂. The successful production of a native-like functional SC and determination of its structure illustrate the characteristics of membrane-confined and membrane-external respiratory electron transport pathways in Gram-negative bacteria.

SUBMITTER: Steimle S 

PROVIDER: S-EPMC7876108 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature