The structural insights of L-asparaginase from Pseudomonas aeruginosa CSPS4 at elevated temperatures highlight its thermophilic nature

Abstract

In the present investigation, a novel thermophilic L-asparaginase (Asn_PA) from Pseudomonas aeruginosa CSPS4 was investigated to explore its structural insights at elevated temperatures. Sequence analysis of Asn_PA depicted three conserved motifs (VVILATGGTIAG, DGIVITHGTDTLEETAYFL, and, LRKQGVQIIRSSHVNAGGF), of them, two motifs exhibit catalytically-important residues i.e., T⁴⁵ and T¹²⁵. A homology modelling-based structure model for Asn_PA was generated with 4PGA as the top-matched template. The predicted structure was validated and energy was minimized. Molecular docking was carried out cantered at the active site for asparagine and glutamine as its substrate ligands. The enzyme–substrate interaction analysis showed binding affinities of – 4.8 and – 4.1 kcal/mol for asparagine and glutamine respectively. Molecular dynamics (MD) simulation studies showed a better stability of Asn_PA at temperatures of 60 °C, over 40, 50 and, 80 °C, making this enzyme a novel L-asparaginase from other mesophilic P. aeruginosa strain. The trajectory analysis showed that RMSD, Rg, and, SASA values correlate well with each other in the different tested temperatures during the MD analysis. Thus, the present findings encourage extensive characterization of the Asn_PA using laboratory experiments to understand the structural behavior of the active site loop in an open or closed state with and without the substrate molecules.