engleski

Molecular dynamics simulations of interaction between FNR and TROL proteins included in final step of photosynthetic electron transfer

The final step of photosynthetic electron transfer from ferredoxin to NADP+ is catalysed by ferredoxin:NADP+ oxidoreductase (FNR). [1] This photosynthetic electron transport produces reductive power that is utilised by various enzymes involved in both chloroplast and cellular metabolism. Localization of the FNR on the chloroplastic membrane is attained by both, the dynamic interaction via thylakoid rhodanese-like protein (TROL), and with the lasting interaction with the Tic62 protein. With goal of understanding molecular basis of these interactions at different pH, computational simulations were applied. Starting from available crystal structure of the FNR dimer in complex with ITEP domain [2], various systems consisted of the FNR proteins and the FNR binding domains (ITEP) from the TROL and Tic62 proteins were built in silico. Systems were subjected to molecular dynamics (MD) simulations at three different pH (6, 7 and 8). Results of simulations enabled identification of the most important regions of noncovalent interactions between involved proteins and their detailed mapping. In order to validate the results of initial simulations of the systems consisted only of wild type (WT) proteins, in silico mutations were introduced into the ITEP domain of TROL protein and further subjected to MD simulations. Influence of the introduced mutations to the structural properties, dynamics and stability of the protein complexes were studied. Results of MD simulations enabled identification and detailed analysis of the interface regions between the FNR proteins which consists mostly of hydrophobic interactions. Simulations shown that these regions are under strong influence of the ITEPs conserved proline and serine residues (PPS region). In conclusion, five functionally important hydrogen bond networks that span over the major structural elements of the involved proteins were identified by MD simulations and characterized in details. Three of them show pH dependence and might serve as the pH regulated switches for conformational changes of the protein complex. Histidine residues were identified as crucial for pH sensitivity of identified H-bond networks.

molecular dynamics simulations, FNR

nije evidentirano