Structures of large macromolecular machineries were for long time not studied at atomic level as they were often too large for X-ray crystallography and as electron microscopy was not allowing good enough resolution. In the last decade, however, tremendous progress has been achieved in the field of single particle cryo electron microscopy (cryo-EM), which became the method of choice to structurally characterize such large protein complexes. The goal of this BAG is to determine structures of complex and often dynamic protein machineries including multi-subunit complexes, protein-nucleic acid complexes or membrane protein complexes using cryo-EM. The projects aim at determining structures of macromolecular machineries involved in energy conversion and cellular respiration, in nitrate and ammonium metabolism, in ribosome and ribosome-associated functions and in DNA damage repair and maintenance.