Background: Human urate transporter 1 (hURAT1)
is the most pivotal therapeutic target for treating hyperuricemia.
However, the molecular interactions between uric acid and URAT1 are
still unknown due to lack of structural details. Methods: In the present study, several methods (homology modeling, sequence
alignment, docking, and mutagenesis) were used to explain the atomistic
mechanisms of uric acid transport of hURAT1. Results: Residues W357-F365 in the TMD7 and P484-R487 in the TMD11 present
in the hURAT1 have unique roles in both binding to the uric acid and
causing subsequent structural changes. These residues, located in
the transport tunnel, were found to be related to the structural changes,
as demonstrated by the reduced Vmax values
and an unaltered expression of protein level. In addition, W357, G361,
T363, F365, and R487 residues may confer high affinity for binding
to uric acid. An outward-open homology model of hURAT1 revealed a
crucial role for these two domains in the conformational changes of
hURAT1. F241 and H245 in TMD5, and R477 and R487 in TMD11 may confer
high affinity for uric acid, and as the docking analysis suggests,
they may also enhance the affinity for the inhibitors. R477 relation
to the structural changes was demonstrated by the Vmax values of the mutants and the contribution of positive
charge to the uric acid selectivity. Conclusions:
W357-F365 in TMD7, P484-R487 in TMD11, and residues F241, H245, and
R477 were found to be critical for the translocation and recognition
of uric acid.