title: Participation of chlorobiumquinone in the transplasma membrane electron transport system of Leishmania donovani promastigote: effect of near-ultraviolet light on the redox reaction of plasma membrane.
abstract: The respiratory quinone composition of the parasitic protozoa Leishmania donovani promastigote was investigated. 1'-oxomenaquinone-7, a chlorobiumquinone was found to be the major isoprenoid quinone. Substantial level of ubiquinone-9 was also present. Isolation and identification of the quinone from the purified plasma membrane yielded mainly 1'-oxomenaquinone-7 and ubiquinone-9; menaquinone was not detected. Membrane bound 1'-oxomenaquinone-7 could be destroyed by near-ultraviolet irradiation, with a concomitant loss or stimulation of plasma membrane electron transport activities. The abilities of different quinones to restore alpha-lipoic acid and ferricyanide reductase activity in near UV-irradiated cell preparations were compared. The order was; conjugate of chlorobiumquinone and sphingosine base approximately conjugate of 2-methyl-3-(1'-oxooctadecyl)-1,4-napthoquinone and octadecylamine >> chlorobiumquinone approximately 2-methyl-3-(1'-oxooctadecyl)-1,4-napthoquinone > menaquinone-4 approximately ubiquinone-10. After irradiation with near-UV light, transmembrane alpha-lipoic acid reduction was inhibited, while transmembrane ferricyanide reduction was stimulated. The result obtained indicates that chlorobiumquinone mediates the plasma membrane electron transport between cytosolic reductant and oxygen as well as alpha-lipoic acid. UV-inactivation of chlorobiumquinone shuts down the plasma membrane oxygen uptake and diverts the electron flux towards ferricyanide reduction via ubiquinone-9. Chlorobiumquinone is the only example of a polyisoprenoid quinone containing a side chain carbonyl group from photosynthetic green-sulphur bacteria. Recent work has revealed numerous genes of trypanosomatid sharing common ancestry with plants and/or bacteria. These observations pose some fascinating questions about the evolutionary biology of this important group of parasitic protozoa.
authors.affiliation: Division of Medicinal Biochemistry, Department of Pharmaceutical Technology, Jadavpur University, Kolkata 700032, India.
authors.forename: Shibendu
authors.initials: S
authors.lastname: Biswas
authors.forename: Rabiul
authors.initials: R
authors.lastname: Haque
authors.forename: Nihar R
authors.initials: NR
authors.lastname: Bhuyan
authors.forename: Tanmoy
authors.initials: T
authors.lastname: Bera
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects* / Q000528:radiation effects*; D004579:Electron Transport / Q000528:radiation effects; D007893:Leishmania donovani / Q000378:metabolism* / Q000528:radiation effects*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010084:Oxidation-Reduction / Q000528:radiation effects; D008063:Thioctic Acid / Q000378:metabolism; D014466:Ultraviolet Rays; D024482:Vitamin K 2 / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism
chemical_list: C527884:1'-oxomenaquinone-7; D024482:Vitamin K 2; D008063:Thioctic Acid; D009247:NADH, NADPH Oxidoreductases; C014227:ferricyanide reductase