Metalloproteases are the second-largest group of proteolytic enzymes and are synthesized by all organisms. Bacteria utilize metalloproteases for many different purposes, such as digestion of nutrients, virulence factors cleaving host or endogenous proteins, or proteostasis, to name just a few examples. The highly specific proline-proline endopeptidases (PPEPs), which were first described for C. difficile, catalyse hydrolysis of the peptide bond between two proline residues, which represents a very unusual cut that is only described 47 times in the MEROPS data base. The talk will discuss how PPEPs recognize their substrates and achieve their exquisite specificity. While PPEPs very selectively clip their (endogenous) substrates at a few sites, the ATP-dependent and membrane-spanning protease FtsH serves for membrane protein quality control but also targets cytosolic proteins. It controls the lifetime of key regulators in LPS biosynthesis, transcription, and heat shock response. We have published in the past crystal structures of truncated, partially active FtsH constructs in the ADP-bound and nucleotide-free state. While these crystal structures provided valuable insight into the architecture and potential substrate translocation mechanisms, a full-length structure is needed for a better (possibly full) picture of its modus operandi. We have determined cryoEM structures of full-length FtsH in the ATP and ADP-bound state and will describe the results.