title: The structure of Plasmodium falciparum serine hydroxymethyltransferase reveals a novel redox switch that regulates its activities.
abstract: Plasmodium falciparum serine hydroxymethyltransferase (PfSHMT), an enzyme in the dTMP synthesis cycle, is an antimalarial target because inhibition of its expression or function has been shown to be lethal to the parasite. As the wild-type enzyme could not be crystallized, protein engineering of residues on the surface was carried out. The surface-engineered mutant PfSHMT-F292E was successfully crystallized and its structure was determined at 3 Å resolution. The PfSHMT-F292E structure is a good representation of PfSHMT as this variant revealed biochemical properties similar to those of the wild type. Although the overall structure of PfSHMT is similar to those of other SHMTs, unique features including the presence of two loops and a distinctive cysteine pair formed by Cys125 and Cys364 in the tetrahydrofolate (THF) substrate binding pocket were identified. These structural characteristics have never been reported in other SHMTs. Biochemical characterization and mutation analysis of these two residues confirm that they act as a disulfide/sulfhydryl switch to regulate the THF-dependent catalytic function of the enzyme. This redox switch is not present in the human enzyme, in which the cysteine pair is absent. The data reported here can be further exploited as a new strategy to specifically disrupt the activity of the parasite enzyme without interfering with the function of the human enzyme.
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Penchit
authors.initials: P
authors.lastname: Chitnumsub
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Wanwipa
authors.initials: W
authors.lastname: Ittarat
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Aritsara
authors.initials: A
authors.lastname: Jaruwat
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Krittikar
authors.initials: K
authors.lastname: Noytanom
authors.affiliation: Department of Biochemistry and Center for Excellence in Protein Structure and Function, Faculty of Science, Mahidol University, Bangkok, Thailand.
authors.forename: Watcharee
authors.initials: W
authors.lastname: Amornwatcharapong
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Wichai
authors.initials: W
authors.lastname: Pornthanakasem
authors.affiliation: Department of Biochemistry and Center for Excellence in Protein Structure and Function, Faculty of Science, Mahidol University, Bangkok, Thailand.
authors.forename: Pimchai
authors.initials: P
authors.lastname: Chaiyen
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Yongyuth
authors.initials: Y
authors.lastname: Yuthavong
authors.affiliation: National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
authors.forename: Ubolsree
authors.initials: U
authors.lastname: Leartsakulpanich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003460:Crystallization; D012696:Glycine Hydroxymethyltransferase / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010963:Plasmodium falciparum / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D012696:Glycine Hydroxymethyltransferase
keywords: Plasmodium falciparum; antimalarial target; disulfide/sulfhydryl switch; protein engineering; serine hydroxymethyltransferase