Investigating the folding pathway and substrate induced conformational changes in B. malayi Guanylate kinase

- Detailed biophysical characterization of BmGK carried out for the first time.
- Folding pathway of BmGK is altered upon binding of substrates (GMP & ATP).
- Binding of substrates stabilises BmGK.
- The binding interaction of Arg145 with GMP shows a switch over to ATP after 40 ns simulation of BmGK-GMP-ATP ternary complex.
- Addition of ATP also results in increase in fluctuation in BmGK-GMP-ATP complex in the region from 130 to 150 residues.

Guanylate kinase is one of the key enzymes in nucleotide biosynthesis. The study highlights the structural and functional properties of Brugia malayi Guanylate kinase (BmGK) in the presence of chemical denaturants. An inactive, partially unfolded, dimeric intermediate was observed at 1-2 M urea while GdnCl unfolding showed monomer molten globule like intermediate at 0.8-1.0 M. The results also illustrate the protective role of substrates in maintaining the integrity of the enzyme. The thermo stability of protein was found to be significantly enhanced in the presence of the substrates. Furthermore, binding of the substrates, GMP and ATP to BmGK changed its GdnCl induced unfolding pattern. Docking and molecular dynamic simulation performed for native BmGK, BmGK bound to GMP and GMP + ATP showed change in the fluctuation in the region between 130 and 150 residues. Arg134 lost its interaction with GMP and Arg145 interaction shifted to ATP after 40 ns simulation upon binding of ATP to BmGK-GMP complex. We, thus, propose the importance of specific rearrangements contributed by binding of substrates which participate in the overall stability of the protein. The work here emphasizes on detailed biophysical characterization of BmGK along with the significant role of substrates in modulating the structural and functional properties of BmGK.