[Progress on structural biology of voltage-gated ion channels].

Ion channels mediate ion transport across membranes, and play vital roles in processes of matter exchange, energy transfer and signal transduction in living organisms. Recently, structural studies of ion channels have greatly advanced our understanding of their ion selectivity and gating mechanisms. Structural studies of voltage-gated potassium channels elucidate the structural basis for potassium selectivity and voltage-gating mechanism; structural studies of voltage-gated sodium channels reveal their slow and fast inactivation mechanisms; and structural studies of transient receptor potential (TRP) channels provide complex and diverse structures of TRP channels, and their ligand gating mechanisms. In the article we summarize recent progress on ion channel structural biology, and outlook the prospect of ion channel structural biology in the future.

Rifampicin as a novel tyrosinase inhibitor: Inhibitory activity and mechanism.

In this study, the inhibitory effect and mechanism of rifampicin on the activity of tyrosinase were investigated for developing a novel tyrosinase inhibitor. It was found to have a significant inhibition on the activity of tyrosinase (IC50=90±0.6µM). From the kinetics analysis, it was proved to be a reversible and noncompetitive type inhibitor of the enzyme with the KI value of 94±3.5µM. The results obtained from intrinsic fluorescence quenching indicated that rifampicin could interact with tyrosinase. In particular, the drastic decrease of fluorescence intensity was due to the formation of a rifampicin-enzyme complex in a static procedure which was mainly driven by hydrophobic forces and hydrogen bonding. Moreover, the ANS-binding fluorescence analysis suggested that rifampicin binding to tyrosinase changed the polarity of the hydrophobic regions. Molecular docking analysis further revealed that the hydrogen bonds were generated between rifampicin and amino residues Leu7, Ser52, and Glu107 in the B chain of the enzyme. And the hydrophobic forces produced through the interaction of rifampicin with B chain residues Pro9, Pro14, and Trp106. This work identified a novel tyrosinase inhibitor and potentially contributed to the usage of rifampicin as a potential hyperpigmentation drug.