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
posted on 2019-12-19, 20:14authored byFernanda Mendoza, Gonzalo A. Jaña
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 of as a potential solution to overcome this problem, although
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 they
involve A8, I58, and I62. Although A8 is not part of the loop 51-62,
it turns out to be key to 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.