Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data

and Computer Simulations

Poster Abstracts

152

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

, Cahit Burduroglu

, Osman Ugur Sezerman

Sabancı University, İstanbul, Turkey,

ISOF-CNR, Bologna, Italy,

Acıbadem University,

İstanbul, Turkey,

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.