title: Isolation, characterization, interaction of a thiazolekinase (Plasmodium falciparum) with silver nanoparticles.
abstract: Malaria, a mosquito-borne infectious disease, is caused by the Plasmodium genus, and remains one of the greatest health challenges worldwide. The malarial parasite possess a biosynthetic pathway for the B-group vitamin incorporating the thiamine metabolizing enzymes; humans on the other hand cannot synthesize the vitamin and require it from within their diet. The vitamin B1 biosynthetic enzyme 5-(2-hydroxyethyl)-4-methylthioazolekinase [EC. 2.7.1.50] from Plasmodium (PfThzK) is particularly attractive as a biomedical target since any inhibition of this enzyme may lead to an effective treatment for malaria. In the present study, PfThzK was recombinantly produced as a 6× His fusion protein in Escherichia coli BL21(DE3) and purified using nickel affinity and size exclusion chromatography. The enzyme was monomeric with a molecular mass of 34 kDa, a specific activity of 295.04 nmol min(-1) mg(-1) and showed an optimum temperature and pH of 37 °C and 7.5, respectively. The purified PfThzK was non-competitively inhibited (79%) by silver nanoparticles (2-6 nm); Ki=6.45 μM. A mechanism is suggested for the interaction of the silver nanoparticle with PfThzK through two sulphur bearing amino acids (Met(1), Cys(206)) on the surface of each subunit of the enzyme.
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa.
authors.forename: J
authors.initials: J
authors.lastname: Yao
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa.
authors.forename: J
authors.initials: J
authors.lastname: van Marwijk
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa.
authors.forename: B
authors.initials: B
authors.lastname: Wilhelmi
authors.affiliation: Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa. Electronic address: C.Whiteley@ru.ac.za.
authors.forename: C G
authors.initials: CG
authors.lastname: Whiteley
mesh_terms: D000595:Amino Acid Sequence; D000962:Antimalarials / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D057075:Enzyme Assays; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D013045:Species Specificity; D013831:Thiamine / Q000037:antagonists & inhibitors / Q000096:biosynthesis
chemical_list: D000962:Antimalarials; D021122:Protein Subunits; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D012834:Silver; C108435:4-methyl-5-(beta-hydroxyethyl)thiazole kinase; D017853:Phosphotransferases (Alcohol Group Acceptor); D013831:Thiamine
keywords: 5-(2-Hydroxyethyl)-4-methyl-thioazolekinase; Inhibition; Silver nanoparticles