Supramolecular Organization in Prokaryotic Respiratory Systems

Abstract

Prokaryotes are characterized by an extreme flexibility of their respiratory systems allowing them to cope with various extreme environments. To date, supramolecular organization of respiratory systems appears as a conserved evolutionary feature as supercomplexes have been isolated in bacteria, archaea, and eukaryotes. Most of the yet identified supercomplexes in prokaryotes are involved in aerobic respiration and share similarities with those reported in mitochondria. Supercomplexes likely reflect a snapshot of the cellular respiration in a given cell population. While the exact nature of the determinants for supramolecular organization in prokaryotes is not understood, lipids, proteins, and subcellular localization can be seen as key players. Owing to the well-reported supramolecular organization of the mitochondrial respiratory chain in eukaryotes, several hypotheses have been formulated to explain the consequences of such arrangement and can be tested in the context of prokaryotes. Considering the inherent metabolic flexibility of a number of prokaryotes, cellular distribution and composition of the supramolecular assemblies should be studied in regards to environmental signals. This would pave the way to new concepts in cellular respiration.

An electron transfer path connects subunits of a mycobacterial respiratory supercomplex

“…Phospholipids, especially cardiolipin (CL), are known to contribute to both the assembly and stability of respiratory complexes and supercomplexes (39). In the structure of SC III-IV, phospholipids are identified in the transmembrane space of CIII and CIV and the interface between CIII and CIV ( Fig.…”

How drugs get into cells: tested and testable predictions to help discriminate between transporter-mediated uptake and lipoidal bilayer diffusion

“…The lipid surface area would still be significantly greater than that of the transporter protein.” Counter: The surface area per se is not the question. What matters is the extent to which the presence of high amounts of protein in a cell membrane (Dupuy and Engelman, 2008), often binding specific lipids (Laganowsky et al, 2014) (including cholesterol; Song et al, 2014) and certainly altering their organization (Mitra et al, 2004; Engelman, 2005; Mclaughlin and Murray, 2005; Beswick et al, 2011; Coskun and Simons, 2011; Kusumi et al, 2011; Lee, 2011a,b; Domański et al, 2012; KoldsØ and Sansom, 2012; Magalon et al, 2012; Mueller et al, 2012; Smith, 2012; Goose and Sansom, 2013; Javanainen et al, 2013; Van Der Cruijsen et al, 2013) (and vice versa ; Li et al, 2012; Denning and Beckstein, 2013), alters any ability of drug molecules to cross via the lipoidal bilayer part of the membranes in which these proteins exist. This means that any direct change of lipids will also have the potential likelihood of affecting transporters, so is not of itself a discriminating experiment if transporter activities are not measured.…”

Different Functions of Phylogenetically Distinct Bacterial Complex I Isozymes

“…Unlike what occurs in mitochondria, bacterial electron transport chains are diverse and flexible ( 7 ). Some bacterial aerobic respiratory chains contain homologues of the mitochondrial bioenergetic enzymes (complex I, cytochrome bc 1 , and cytochrome aa 3 ) ( 8 ). In contrast, other bacteria contain one or more quinol oxidases or lack some of the bioenergetic enzymes that are found in mitochondria ( 4 , 8 – 10 ).…”