title: Plasmodium falciparum: nitric oxide modulates heme speciation in isolated food vacuoles.
abstract: Nitric oxide (NO) and NO-derived reactive nitrogen species (RNS) are present in the food vacuole (FV) of Plasmodium falciparum trophozoites. The product of PFL1555w, a putative cytochrome b(5), localizes in the FV membrane, similar to what was previously observed for the product of PF13_0353, a putative cytochrome b(5) reductase. These two gene products may contribute to NO generation by denitrification chemistry from nitrate and/or nitrite present in the erythrocyte cytosol. The possible coordination of NO to heme species present in the food vacuole was probed by resonance Raman spectroscopy. The spectroscopic data revealed that in situ generated NO interacts with heme inside the intact FVs to form ferrous heme nitrosyl complexes that influence intra-vacuolar heme solubility. The formation of heme nitrosyl complexes within the FV is a previously unrecognized factor that could affect the equilibrium between soluble and crystallized heme within the FV in vivo.
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA. osterag@georgetown.edu
authors.forename: Graciela
authors.initials: G
authors.lastname: Ostera
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Tokumasu
authors.forename: Clarissa
authors.initials: C
authors.lastname: Teixeira
authors.forename: Nicolas
authors.initials: N
authors.lastname: Collin
authors.forename: Juliana
authors.initials: J
authors.lastname: Sa
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hume
authors.forename: Sanjai
authors.initials: S
authors.lastname: Kumar
authors.forename: Jose
authors.initials: J
authors.lastname: Ribeiro
authors.forename: Gudrun S
authors.initials: GS
authors.lastname: Lukat-Rodgers
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Rodgers
mesh_terms: D000818:Animals; D003460:Crystallization; D004912:Erythrocytes / Q000469:parasitology; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007106:Immune Sera; D015151:Immunoblotting; D051379:Mice; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D012995:Solubility; D013059:Spectrum Analysis, Raman; D014617:Vacuoles / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007106:Immune Sera; D009569:Nitric Oxide; D006418:Heme