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Albany 2019: 20th Conversation - Abstracts

category image Albany 2019
Conversation 20
June 11-15 2019
Adenine Press (2019)

The distribution of electrostatic surface potentials is an important factor underlying the temperature adaptation of subtilisin-like serine proteases

The molecular mechanisms of enzymatic temperature adaptation are dictated by the delicate balance between the stability, flexibility, and activity of the extremophilic enzymes; therefore, identifying the factors that rule the stability-flexibility-activity relationship is essential for both fundamental research and industrial applications (Papaleo, Tiberti, Invernizzi, Pasi, & Ranzani, 2011). To investigate the role of electrostatics in temperature adaptation, we have performed a comparative study on three differently temperature-adapted subtilisin-like serine proteases, the psychrophilic VPR, the mesophilic PRK, and the thermophilic AQN, using multiple-replica molecular dynamics simulations followed by continuum electrostatics calculations and comparison of electrostatic surface potentials. Comparison of the salt-bridge electrostatic strength at 300 K reveals that they on average provide greater stabilization to VPR and PRK than to AQN, indicating that salt bridge may not be a crucial factor in determining the overall thermostability of subtilisin-like serine proteases. The most significant difference lies in the distribution of different electrostatic surface potentials, especially across the back surfaces, i.e., those of PRK and AQN are dominated by the electro-positive potential with sporadic electro-neutral patches interspersed, and VPR’s back surface is dominated by the electro-negative potential, although the catalytic centers (on the front surface) of the three proteases collectively feature the electro-negative potential. Because water is a protic solvent, it interacts more favorably with the electro-negative surface than with the electro-positive and neutral surfaces, and this explains why a protein with more negative surface charge is more soluble in water than its homologue with more positive surface charge. Furthermore, since water molecules around the negatively charged and polar uncharged surfaces form a high-density, collapsed structure with weak hydrogen-bonding interactions and fast dynamics, they would facilitate conformational fluctuations, hence enhancing the local flexibility of the electro-negative surface regions. On the contrary, the low-density, expanded structure of hydration shell formed around the positively charged and nonpolar/neutral surfaces would restrain their fluctuations and hence increase the local rigidity. For the mesophilic PRK at 300 K, comparison of the Cα root-mean-square-fluctuation values averaged over the solvent-exposed residues covered by the electro-negative, electro-positive, and electro-neutral potentials reveals that the electro-negative surface is indeed more flexible than the electro-positive and nonpolar/neutral surfaces. For all three proteases, the electro-negative surface potential around the active center could provide the active-center flexibility necessary for nucleophilic attack and proton transfer. For VPR, the predominant distribution of the electro-negative potential on the back surface could ensure sufficient low-temperature solubility and surface flexibility crucial for VPR’s low-temperature catalytic activity. For AQN, the predominant distribution of the electro-positive potential likely contributes to enhancing the surface rigidity necessary for the maintenance of the structural integrity at high temperatures. Therefore, differently charged surface patches can affect/modulate via differential interactions with water molecules the protein solubility and the local structural flexibility/rigidity (Xia et al., 2018) and, therefore, the electrostatic surface potential distribution is an important factor underlying the temperature adaptation of subtilisin-like serine proteases .

This research has been supported by NSFC of China (Nos. 31160181 and 31370715) and Programs for Excellent Young Talents and Donglu Scholar in the Yunnan University.

References

    Papaleo, E., Tiberti, M., Invernizzi, G., Pasi, M., & Ranzani, V. (2011). Molecular determinants of enzyme cold adaptation: Comparative structural and computational studies of cold- and warm-adapted enzymes. Current Protein & Peptide Science, 12, 657-683.

    Xia, Y. L., H., S. J., Ai, S. M., Li, Y., Du, X., Sang, P., . . . Liu, S. Q. (2018). Insights into the role of electrostatics in temperature adaptation: a comparative study of psychrophilic, mesophilic, and thermophilic subtilisin-like serine proteases. RSC Advances, 8, 29698-29713.

Yuan-Ling Xia
Xiao-Yan Zhang
Yan Tao
Shu-Qun Liu*

State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan & School of Life Sciences
Yunnan University
Kunming 650091, China

*Email: shuqunliu@gmail.com
Phone: (86)871-65031093