Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations

Poster Abstracts

115-POS Board 35 Modeling Structural Properties and Thermostability of the Active Conformation of Lipase from Geobacillus Thermocatenulatus, BTL2, in Organic Solvent Asli Yenenler 1,4 , Alessandro Venturini 2 , Cahit Burduroglu 3 , Osman Ugur Sezerman 4 . 1 Sabancı University, İstanbul, Turkey, 2 ISOF-CNR, Bologna, Italy, 3 Acıbadem University, İstanbul, Turkey, 4 Acıbadem University, İstanbul, Turkey. Lipase enzymes have been widely used in different fields of biotechnology for many years. Even if they are generally used in aqueous environment for hydrolysis reactions, their usage in organic solvent promises high-level development at industrial level allowing a broad range of different esterification and transesterification reactions. Yet, the presence of organic solvent brings structural and enzymatic limitations to lipases that have to be overcome for their effective usage. In this work, we have investigated the effects of toluene solvent on the structure of BTL2 from Bacillus thermocatenulatus through MD simulations over 30 ns. By comparing the behavior of BTL2 in aqueous and in hydrophobic media, we have detected the parts of the protein more affected by the presence of toluene. In general, the organic solvent increases the rigidity of the enzyme. A significant example of our analysis is the unusual packing of catalytic Ser114. Further, we assess the change in secondary structure and destabilization tendency of BTL2 in the hydrophobic environment with STRIDE analysis and FoldX calculations. These results suggest that the presence of toluene molecules leads to some structural changes that affect the packing of BTL2 and eventually limiting its enzymatic ability. To overcome this problem, we have added a layer of water (5%) around BTL2 to provide the required structural flexibility. Moreover, point mutations like Gly116Pro, Gly116Pro_Gly319Pro (double mutation) and, Glu271Ala, and Asn317Ala to increase structural stability and to provide the required flexibility of the protein, have been carried out. We think that this study will allow further progress in understanding the behavior of these enzymes in organic solvent and then allow their industrial exploitation.

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