In Silico Identification of a Key Residue for Substrate Recognition of the Riboflavin Membrane Transporter RFVT3

Because
of its specific physicochemical properties (fluorescence,
photosensitizing, and redox reactions), vitamin B2, also called riboflavin
(RF), has been generating a lot of interest in the fields of nanotechnology
and bioengineering in the last decade. RF, by targeting its riboflavin
transporters (RFVTs) overexpressed in some cancers, is particularly
used to functionalize nanovectors for anticancer drug delivery. From
a physiopathological point of view, an RF deficiency has been implicated
in various pathologies, including mendelian diseases. RF deficiency
is mainly due to natural variants of its RFVTs that make them inactive
and therefore prevent RF transport. The lack of structural data about
RFVT is a major drawback for a better understanding of the role of
the mutations in the molecular mechanism of these transporters. In
this context, this work was aimed at investigating the 3D structure
of RFVT3 and its interactions with RF. For this purpose, we used an
in silico procedure including protein threading, docking, and molecular
dynamics. Our results propose that the natural variant W17R, known
to be responsible for the Brown-Vialetto-Van Laere syndrome, prevents
the recognition of RF by RFVT3 and thus blocks its transport. This
in silico procedure could be used for elucidating the impact of pathogenic
mutations of other proteins. Moreover, the identification of RF binding
sites will be useful for the design of RF-functionalized nanovectors.