Lukas Denkhaus

Abstract

Periplasmatic c-type cytochromes, containing more than one covalent attached heme group, are wide spread among different strains of bacteria and archaea. They play a role in electron transfer, electron storage and in the catalysis of redox-reactions. In the nitrogen cycle multiheme cytochromes are found in the anammox process, nitrification and dissimilatory nitrite reduction to ammonia (DNRA). The proteins cytochrome c nitrite reductase (NrfA) of the DNRA and hydroxylamine oxidoreductase (HAO) share significant structural similarities, especially the arrangement of the heme groups. It is therefore assumed these proteins are evolutionary related. In the organisms Geobacter metallireducens, Campylobacter concisus and Campylobacter curvus three multiheme cytochromes have been identified which are particular interesting to investigate the evolution of nitrogen cycle multiheme cytochromes. These enzymes share structural homology to HAO and functional homology to NrfA and can therefore be regarded as evolutionary intermediates. Furthermore, the electron donors of these proteins, potentially membrane bound cytochrome c quinol dehydrogenases are investigated in this project.

Methods

Heterologous protein production and purification, enzyme kinetics, stopped-flow UV-vis spectroscopy, X-ray crystallography