Structure of Escherichia coli cytochrome bd-II type oxidase with bound aurachin D
Antonia Grauel, Jan Kägi, Tim Rasmussen, Iryna Makarchuk, Sabrina Oppermann, Aurélien F. A. Moumbock, Daniel Wohlwend, Rolf Müller, Frédéric Melin, Stefan Günther, Petra Hellwig, Bettina Böttcher, Thorsten Friedrich
Abstract
Abstract Cytochrome bd quinol:O 2 oxidoreductases are respiratory terminal oxidases so far only identified in prokaryotes, including several pathogenic bacteria. Escherichia coli contains two bd oxidases of which only the bd -I type is structurally characterized. Here, we report the structure of the Escherichia coli cytochrome bd -II type oxidase with the bound inhibitor aurachin D as obtained by electron cryo-microscopy at 3 Å resolution. The oxidase consists of subunits AppB, C and X that show an architecture similar to that of bd -I. The three heme cofactors are found in AppC, while AppB is stabilized by a structural ubiquinone-8 at the homologous positions. A fourth subunit present in bd -I is lacking in bd -II. Accordingly, heme b 595 is exposed to the membrane but heme d embedded within the protein and showing an unexpectedly high redox potential is the catalytically active centre. The structure of the Q-loop is fully resolved, revealing the specific aurachin binding.