FOR 1220:  Prosthetic Groups: Transport and Insertion - PROTRAIN

• Subject Area: Biology ; Chemistry
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 100799727

Over one third of all proteins contains prosthetic groups, metals and cofactors. These groups are indispensable for catalysis as they form part of the catalytic centre of the enzyme or they are part of intramolecular electron transport. Prosthetic groups are of key importance for a large number of biological reactions, e.g. photosynthesis, energy metabolism, oxygen transport, anabolism and catabolism, redox reactions, cell signalling etc. While the biosynthesis of many prosthetic groups is well understood it is largely unknown how prosthetic groups are directed to various cellular destinations or stored after their synthesis, and how they ultimately find the way into their correct cognate proteins. Intricate mechanisms have to control distribution, trafficking and insertion into proteins as most of these prosthetic groups are extremely fragile and air-sensitive.
Consequently, there must be a plethora of transporters, chelators, metal cofactors, protein folding chaperones, metallochaperones, carrier proteins, storage proteins and insertases involved. The finely tuned interplay of these components ensures the safe transport, even through membranes, the protection and insertion of prosthetic groups into their target proteins. This complex machinery is completely unexplored. It can be assumed that its level of complexity should equal that of the protein trafficking.
Based on our long-standing background in biosynthesis und functionality of prosthetic groups, we focus in Braunschweig with seven projects on the investigation of the unknown molecular strategies for transport and insertion of molybdenum cofactors (Moco) and hemes into enzymes. In close cooperation, a broad spectrum of methods will be employed ranging from genetic, biochemical and structural approaches to chemical synthesis and bioinformatics tools. The main objective of the Research Unit is to fill the gap in our knowledge about (1) what happens with the prosthetic groups heme and Moco subsequent to their biosynthesis, and (2) how is the process of insertion of these groups into their cognate apo-enyzmes catalysed.
We will dissect the single steps of these processes in order to generate a mechanistic understanding of the biochemical, biophysical and cellular processes governing these dynamic phenomena. We envisage the deduction of novel fundamental principles that will allow to understand and to predict these processes at the molecular level both in bacterial and eukaryotic systems.

• DFG Programme: Research Units

Projects

• Antibody Facility: Generation and characterization of monoclonal antibodies directed against protein motifs involved in binding prosthetic groups (Applicant Jockusch, Brigitte M. )
• Atomic structures and reaction mechanisms of proteins involved in transfer and insertion of molybdenum cofactor and heme (Applicant Heinz, Dirk )
• Central Coordination Project (Applicant Mendel, Ralf R. )
• (i) Identification of single-molecule protein complexes involved in cellular transport of prosthetic groups (Moco and heme) (ii) Generation of monoclonal antibodies directed against protein motifs involved in binding prosthetic groups (Applicant Tinnefeld, Philip )
• Incorporation of the prosthetic heme group into cytoplasmatic and membrane proteins (Applicant Jahn, Dieter )
• Insertion of tetrapyrrole cofactors into cytochrome cd1 nitrite reductase (Applicant Layer, Gunhild Monika )
• Local chemical probes for the investigation of heme transfer processes (Applicant Bröring, Martin )
• Mechanism of insertion of prosthetic groups into complex molybdo-enzymes (molybdo-iron-flavo enzymes) (Applicant Schwarz, Günter )
• Photoaffinity labeling of heme proteins with chemically modified prosthetic groups (Applicant Lindel, Thomas )
• The mechanism of molybdenum cofactor-insertion into apo-enzymes of the sulfite oxidase-class (Applicant Mendel, Ralf R. )
• The molybdo-proteome of N. crassa mitochondria (Applicant Jänsch, Lothar )

• Spokesperson: Professor Dr. Ralf R. Mendel