br Experimental section br Notes br PDB ID
PDB ID codes The atomic coordinates and structure factors of hDHODH in complex with compounds 4 (PDB id: 5MVC), 5 (PDB id: 5MVD) and 6 (PDB id: 5MUT) have been deposited in the RCSB Protein Data Bank.
Acknowledgements This research was financially supported by the University of Turin (Ricerca Locale grant 2015 (LOLMAUTO00) and 2014 (LOLM_RIC_LOC_14_01)). CHA and RCB received financial support from (LOLM_RIC_LOC_14_01) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil, 481392/2013-0) and Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG, Brazil, 201210267001112 and 201310267001105). RF and MA acknowledge support from ESS & MAXIV: Cross Border network and postgraduate education programme MAX4ESSFUN. CHA is CNPq productivity fellow (310025/2015-0) and PG is long term EMBO fellow (ALTF 1163-2014). A-CM is thankful for a grant from the Equal Opportunities Commission of the Faculty of Chemistry of Bielefeld University. RCB and CHA would like to thank ChemAxon for providing the academic license of their software, as well as Brazilian funding agencies CNPq, CAPES and FAPEG.
Malaria is caused by five species of apicomplexan Caffeine of the genus that affect humans. The most deadly form is caused by . and predominates in Africa, whereas . is less dangerous but more widespread. In 2013, 198 million cases were estimated to have occurred globally, and the disease killed 367,000 to 755,000 people , with children under 5 years of age and pregnant women being most severely affected. Resistance to artemisinins—the key compounds in artemisinin-based combination therapies—has been detected in five countries of Southeast Asia: Cambodia, the Lao People\'s Democratic Republic, Myanmar, Thailand, and Viet Nam. Although such resistance has not yet led to operational failure of malaria control programs, urgent and intensified efforts are required to prevent a future public health disaster and new and differentiated treatments are needed. Several antimalarial drugs in clinical studies target pyrimidine nucleotide biosynthesis , because parasites rely on fast and large replication of DNA to infect during liver and blood stages. Dihydroorotate dehydrogenase (DHODH) catalyzes the oxidation of -dihydroorotate (L-DHO) to -orotate in the fourth step in the de novo pyrimidine biosynthetic pathway. It is essential for species survival because, unlike humans, malaria parasites are unable to scavenge preformed pyrimidines . This is the only redox and rate-limiting step in uridine monophosphate (UMP) formation, the precursor to all the other pyrimidines used to synthesize DNA, RNA, and various cofactors . DHODH (DHODH) belongs to family 2, found in gram-negative bacteria and eukaryotes. The enzyme is attached to the inner mitochondrial membrane and contains a tightly bound flavin mononucleotide (FMN) cofactor that is reduced on L-DHO oxidation to -orotate in the first half of the reaction cycle. This cofactor is recycled to its oxidized form in the second half of the reaction, transferring the electrons to the ubiquinone (CoQ) that acts as natural final electron acceptor, chemically coupling pyrimidine biosynthesis to the respiratory chain . One key function of the parasite mitochondrion is to maintain the mitochondrial electron transport chain (mETC) to regenerate the CoQ required as electron acceptor for DHODH. This is demonstrated by the fact that parasites are very sensitive to mETC inhibitors, but transgenic strains expressing ubiquinone-nondependent DHODH from are resistant to them. These results provide a genetic validation of DHODH as an attractive antimalarial target . Potent inhibitors of the human enzyme, such as lapachol, brequinar, and leflunomide, are poorly active against DHODH. Thus, these data suggest that it should be feasible to exploit active-site differences to identify inhibitors that exhibit a high degree of selectivity toward malarial DHODH . The sequence of the L-DHO binding site is highly conserved, but the sequence of the quinone-binding N-terminal domain is variable . This variability is thought to be responsible for the high degree of species-related preferential inhibition observed among DHODH family 2 members. So, therapeutic agents, both those targeted to rapidly proliferating human cells and those targeted to human pathogens, could be designed to explicitly exploit these differences.