N-Terminus Plays a Critical Role for Stabilizing the Filamentous Assembly and the Antifungal Activity of Bg_9562

Abstract

Bg_9562, a prophage tail-like protein was earlier shown to be required for bacterial mycophagy by Burkholderia gladioli strain NGJ1. The purified protein exhibited broad-spectrum antifungal activity; however, the structural and mechanistic details vis-à-vis its activity remained elusive. In this study, we have structurally characterized the protein Bg_9562 using negatively stained transmission electron microscopy, molecular modeling and mutagenesis. We find that Bg_9562 shows structural similarity to Gp13, a tail assembly chaperone. The transmission electron microscopy revealed that, Bg_9562 forms long flexible tubular structures. Molecular modeling of the filament like structure divulges that the inter subunit contacts are meditated largely through hydrophobic interactions. Using mutagenesis, we demonstrate that the N-terminal residues of the protein when deleted results in reduced activity and destabilization of filament formation. Overall, structure-function analysis opens up avenues for further utilization of the protein as a potent antifungal molecule.