Abstract
Luciferase is the key component of light production in bioluminescence process. Extensive and advantageous application of this enzyme in biotechnology is restricted due to its low thermal stability. Here we report the effect of heating up above Tm on the structure and dynamical properties of luciferase enzyme compared to temperature at 298 K. In this way we demonstrate that the number of hydrogen bonds between N- and C-domain is increased for the free enzyme at 325 K. Increased inter domain hydrogen bonds by three at 325 K suggests that inter domain contact is strengthened. The appearance of simultaneous strong salt bridge and hydrogen bond between K529 and D422 and increased existence probability between R533 and E389 could mechanistically explain stronger contact between N- and C-domain. Mutagenesis studies demonstrated the importance of K529 and D422 experimentally. Also the significant reduction in SASA for experimentally important residues K529, D422 and T343 which are involved in active site region was observed. Principle component analysis (PCA) in our study shows that the dynamical behavior of the enzyme is changed upon heating up which mainly originated from the change of motion modes and associated extent of those motions with respect to 298 K. These findings could explain why heating up of the enzyme or thermal fluctuation of protein conformation reduces luciferase activity in course of time as a possible mechanism of thermal functional inactivation. According to these results we proposed two strategies to improve thermal stability of functional luciferase.
Highlights
The process of light emission through chemical reaction in living organisms is called bioluminescence
The structural model of luciferase in free enzyme form was built by comparative homology modeling, S1 Fig. For free enzyme modeling three incomplete reported crystal structure of Photinus pyralis luciferase, with Protein Data Bank (PDB) codes 1BA3, 1LCI and 3IEP, were used as templates. 1BA3 has both N- and C-terminal domains and lacks residues between S198 and S201, a region in N-terminal domain and in the interface between two domains
Root Mean Square Deviation (RMSD) criterion was used to evaluate the structural similarity between model and templates
Summary
The process of light emission through chemical reaction in living organisms is called bioluminescence. Bioluminescent organisms are a diverse group including bacteria, fungi, algae, fish, squid, shrimp, and insects [1]. Luciferase is a general name of the enzymes that catalyze the oxidative reaction of light production. Luciferase structure, its substrate and cofactors varies in these organisms and it seems the bioluminescent systems have developed independently from different evolutionary origins [2].
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