MOLECULAR DYNAMIC SIMULATIONS OF THE COMPLETE GUMB PROTEIN, INVOLVED IN XANTHAN GUM BIOSYNTHESIS

MELINA JACOBS; LUIS IELPI; SILVINA ROSA SALINAS; ROSETTI CARLA MARIANA

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

The outer membrane protein GumB is involved in the synthesis/secretion of the exopolysaccharide xantan in Xanthomonas campestris.Crystals of native protein and its Se-Met derivative were obtained, allowing the determination of Gum tetrameric structure. The electostatic surface representation of GumB tetramer shows it has two identical patches of positive residues delimiting a cavity possibly involved in xanthan binding. The structure of the 25 N-terminal residues were not unraveled in the crystal. The N-terminal residues could be localized dynamically in the cavity.We modeled the N-terminal residues by two methods:i) by folding the N-terminal aminoacids into a polyproline II (PPII) helix, and ii) we constructed an automated model using Wza (a well-studied GumB homolog) as template.Models were submitted to minimization and MD simulation using gromos53A6 ff and GROMACS package. The protein conformation observed in the crystal structure is stable during the simulation. The N-terminal regions are observed to move freely and approaching the protein surface along the simulations