Project description:Electron transfer in respiratory chains generates the electrochemical potential that serves as the energy source for ATP synthesis, solute transport and motility. In eukaryotes and many bacteria, the respiratory chain consists of four electron transport complexes, known as complex I to IV. Respiratory chains of some prokaryotes differ in composition and organization. They can use a wide range of electron donors and acceptors and may have complexes performing the same catalytic reaction. The diversity and apparent redundancy of prokaryotic respiratory chains reflects the versatility and robustness of the organisms. Many of these alternative respiratory chain complexes are either unknown or their structures and mechanisms remain elusive. In this work we describe a 3.9 A cryo-EM structure of the alternative complex III (ACIII) from Rhodothermus marinus, which we demonstrated takes over the role of canonical respiratory complex III (bc1 complex), even though it is structurally unrelated. Our structure reveals that ACIII is an integral membrane protein complex of at least 7 subunits (ActABCDEFH). The periplasmic domain, with ActA, B, E and H, harbours four iron-sulphur clusters and six C-type hemes. The cofactors form two electron wires that converge on the putative quinol-binding site in subunit ActC. The two homologous subunits, ActC and ActF, each have two four-helix bundles in the membrane, with several conserved polar residues that delineate putative proton channels. ACIII meets all requirements for an energy-transducing machine that couples electron transfer from quinol to the oxygen reductase, to translocation of protons across the membrane.
Project description:Perkinsus marinus is an intracellular parasitic protozoan that is responsible for serious disease epizootics in marine bivalve molluscs worldwide and along with P. olseni belongs to the OIE list of notified diseases. Despite all available information on P. marinus genomics, more baseline data is required at the proteomic level for a better understanding of P. marinus biological processes, including virulence mechanisms. In the present study, we have established in vitro clonal cultures of P. marinus from infected gills and mantle tissues of C. rhizophorae to evaluate the parasite cellular proteomic profile. A high throughput label-free shotgun HDMS approach using nanoUPLC-MS was used. Our intention was to provide the first comprehensive proteome profile of P. marinus that might serve as a valuable resource for future investigations involving comparative analyses of P. marinus from different regions, as well as comparisons of different species of Perkinsus.
