The aim of this project funded by DFG includes the determination of X-ray structures of H4MPT dependent enzymes of the methanogenic pathway in complex with H4MPT (or derivatives of H4MPT). We succeeded in a ternary complex structure of the two enzymes that provide valuable Informafion ofthe complex ring structure of H4MPT and allowed the postulation of a structure-based enzymatic mechanism. Both studies are either published already or in the revision process. For a third enzyme we have solved the Mch-formyl-H4MPT complex but need better data and also a Mch-methenyl-H4MPT+ structure to publish in a highranking journal. But the data would be already sufficient for a small publication. Mtr is an extremely difficult long-term project where we hoped at the beginning to produce more result. But the "soluble" subunits of the huge membrane protein complex were extremely delicate and a structure determination of MtrA or MtrH was not feasible. However, first promising results of the EM studies exist and a low-resolution structure can be expected in the future (if the project is continuously funded).