Unveiling the Dynamical and Structural Features That Determine the Orientation of the Acceptor Substrate in the Landomycin Glycosyltransferase LanGT2 and Its Variant with C Glycosylation Activity
Many bioactive compounds are O glycosylated metabolites, however the hydrolytic sensitivity of O glycosidic linkage limits their therapeutic applications. Enzymatically and chemically stable C glycosidic bonds are thought as a potential solution to overcome this problem, though, the insufficient information about the structural preferences and interactions that distinguish the C from the O glycosylation reactions has hindered the development of enzyme engineering strategies. Thus, in this work, the O Glycosyltransferase LanGT2 (O LanGT2) and its engineered C C bond forming variant (C LanGT2) which catalyze the initial glycosylation step in the biosynthesis of the antibiotic landomycin A, were studied by means of all atom Molecular Dynamics simulations. Our results indicate that precise positioning of the acceptor substrate tetrangulol (TET) seems to be determined by the flexibility of the loop 51 62, which gives rise to slightly different secondary structural elements that modulate the interactions between this loop and TET. In O LanGT2, the most notable interactions between TET and the loop 51 62 involve R59 and A62, whereas in C LanGT2 involve A8, I58 and I62. Though A8 is not part of the loop 51 62, turns out to be key on the binding mode exhibited by TET in C LanGT2. Thus, the TET A62 (O LanGT2) and TET A8 (C LanGT2) interactions appear to be critical to accomplish the O and the C glycosidic bond specificity, respectively. Finally, all results together shed light on the molecular basis governing the O and C bond specificity, revealing that the underlying molecular mechanism that tunes the orientation of TET at its binding pocket involves hydrophobic interactions.
J. Chem. Inf. Model.