Cantharidin, a monoterpene isolated from the insect blister beetle, has long been used as a medicinal agent in the traditional Chinese medicine. Cantharidin inhibits a subgroup of serine/threonine phosphatases, thus inducing cell growth inhibition and cytotoxicity. Cantharidin has anticancer activity in vitro, since it is able of inducing p53-dependent apoptosis and double-strand breakage of DNA in cancer cells. Although the toxicity of cantharidin to the gastrointestinal and urinary tracts prevents its medical use, it is a promising lead compound for chemical modification to develop new anticancer therapeutics. In fact, cantharidin does not cause myelosuppression and displays anticancer activity against cells with a multidrug resistance phenotype. Here, the competitive inhibitory effect of cantharidin on heme-Fe(III) binding to the fatty acid site 1 (FA1) of human serum albumin (HSA) is reported. Docking and molecular dynamics simulations support functional data indicating the preferential binding of cantharidin to the FA1 site of HSA. Present results may be relevant in vivo as HSA could transport cantharidin, which in turn could affect heme-Fe(III) scavenging by HSA.
a b s t r a c tA bacterial homologue of the human iron exporter ferroportin found in the predatory Gram-negative bacterium Bdellovibrio bacteriovorus has been investigated. Molecular modelling, expression in recombinant form and iron binding and transport assays demonstrate that B. bacteriovorus ferroportin (bdFpn) is indeed an orthologue of human ferroportin. Key residues corresponding to those essential for iron binding and transport in human ferroportin are conserved in the bacterial homologue and are predicted to be correctly clustered in the central cavity of the protein. Mutation of these residues grossly affects the iron binding and transport ability of bdFpn.
Butylated hydroxytoluene (BHT) is one of the most commonly used synthetic antioxidants in food, cosmetic, pharmaceutical and petrochemical products. BHT is considered safe for human health; however, its widespread use together with the potential toxicological effects have increased consumers concern about the use of this synthetic food additive. In addition, the estimated daily intake of BHT has been demonstrated to exceed the recommended acceptable threshold. In the present work, using BHT as a case study, the usefulness of computational techniques, such as reverse screening and molecular docking, in identifying protein–ligand interactions of food additives at the bases of their toxicological effects has been probed. The computational methods here employed have been useful for the identification of several potential unknown targets of BHT, suggesting a possible explanation for its toxic effects. In silico analyses can be employed to identify new macromolecular targets of synthetic food additives and to explore their functional mechanisms or side effects. Noteworthy, this could be important for the cases in which there is an evident lack of experimental studies, as is the case for BHT.
Ferroportin (Fpn) is a membrane protein representing the major cellular iron exporter, essential for metal translocation from cells into plasma. Despite its pivotal role in human iron homeostasis, many questions on Fpn structure and biology remain unanswered. In this work, we present two novel and more reliable structural models of human Fpn (hFpn; inward-facing and outward-facing conformations) obtained using as templates the recently solved crystal structures of a bacterial homologue of hFpn,
Members of the major facilitator superfamily of transporters (MFS) play an essential role in many physiological processes such as development, neurotransmission, and signaling. Aberrant functions of MFS proteins are associated with several diseases, including cancer, schizophrenia, epilepsy, amyotrophic lateral sclerosis and Alzheimer’s disease. MFS transporters are also involved in multidrug resistance in bacteria and fungi. The structures of most MFS members, especially those of members with significant physiological relevance, are yet to be solved. The lack of structural and functional information impedes our detailed understanding, and thus the pharmacological targeting, of these transporters. To improve our knowledge on the mechanistic principles governing the function of MSF members, molecular dynamics (MD) simulations were performed on the inward-facing and outward-facing crystal structures of the human ferroportin homologue from the Gram-negative bacterium Bdellovibrio bacteriovorus (BdFpn). Several simulations with an excess of iron ions were also performed to explore the relationship between the protein’s dynamics and the ligand recognition mechanism. The results reinforce the existence of the alternating-access mechanism already described for other MFS members. In addition, the reorganization of salt bridges, some of which are conserved in several MFS members, appears to be a key molecular event facilitating the conformational change of the transporter.
Ferroportin, a membrane protein belonging to the major facilitator superfamily of transporters, is the only vertebrate iron exporter known so far. Several ferroportin mutations lead to the so-called ferroportin disease or type 4 hemochromatosis, characterized by two distinct iron accumulation phenotypes depending on whether the mutation affects the activity of the protein or its degradation pathway. Through extensive molecular modeling analyses using the structure of all known major facilitator superfamily members as templates, multiple structural models of ferroportin in the three mechanistically relevant conformations (inward open, occluded, and outward open) have been obtained. The best models, selected on the ground of experimental data available on wild-type and mutant ferroportion, provide for the first time a prediction at the atomic level of the dynamics of the transporter. Based on these results, a possible mechanism for iron export is proposed.
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