Identification of Fusarium Moniliformin PG Inhibitor using Comparitive Bioinformatics Studies of PGIP of Pharsalus vulgaris and its Neighbours of LRR Superfamily

Abstract

Invasion of the Phytopathogenic organisms such as fungi, bacteria, virus and nematodes which disrupt the cell wall of the plant by secreting their pectin degrading PolyGalacturonase (PG) enzyme is evaded by the interaction of plant PolyGalacturonase-Inhibiting Proteins (PGIPs). PGIP from Pharsalus vulgaris is reported to blocks the attack of many pathogens, most importantly Fusarium moniliforme. The two PGIP isoforms, PGIP1 and PGIP2 sharing 99% sequence identity show differential activity towards FmPG. PGIP2 blocks FmPG while PGIP1 is unable to do so, while both these proteins belong to the same multigame family. PG-inhibitory activity is also shown by PGIPs of other plant species. Identification of sequence homolog’s of PvPGIP2, sequence similarity of at least 50%, through BLAST followed by MSA and nearest neighbour analysis suggests Glycine max(Soybean) and Pisum sativum(Pea) to be close relatives of Pharsalus vulgaris (Kidney Bean). As already known GmPGIP3 effectively evades infection caused by Fusarium moniliforme blocking its PG enzyme while in Pea the efficacy of PGIP1 against FmPG is yet to be explored. Pairwise sequence comparisons and structure modeling of PvPGIP1 and PsPGIP1 is followed by prediction of putative binding sites of the fungal enzyme FmPG by CASTp. A comparative analysis is then drawn by docking the three PGIP proteins from Kidney Bean (PvPGIP2 and PvPGIP1) and Pea (PsPGIP1) respectively with FmPG using GRAMM-X server. It brings into light that PsPGIP1-FmPG shows same mode of binding as PvPGIP2-FmPG complex despite of being less similar at sequence level. Further on, the residues involved in hydrophobic and ionic interaction are calculated for all the three docked complexes involving FmPG and PGIP proteins from Pharsalus vulgaris (PvPGIP1 and PvPGIP2) and Pisum sativum(PsPGIP1) by PIC. The docking results reveal that PsPGIP1 from Pisum sativum blocks the active cleft of the fungal enzyme FmPG inhibiting the enzyme in similar way as shown by PGIP2 from Pharsalusvulgarisalso the outcomes obtained from the interaction analysis suggest that since same residues of the enzyme FmPG are involved in hydrophobic and ionic interactions in the FmPG-PvPGIP2 complex and FmPG-PsPGIP1 thus PsPGIP1 from Pisum sativumis able to block Polygalacturonase enzyme (FmPG) from Fusarium moniliformin.