title: Ferrous ion transport across chloroplast inner envelope membranes.
abstract: The initial rate of Fe(2+) movement across the inner envelope membrane of pea (Pisum sativum) chloroplasts was directly measured by stopped-flow spectrofluorometry using membrane vesicles loaded with the Fe(2+)-sensitive fluorophore, Phen Green SK. The rate of Fe(2+) transport was rapid, coming to equilibrium within 3s. The maximal rate and concentration dependence of Fe(2+) transport in predominantly right-side-out vesicles were nearly equivalent to those measured in largely inside-out vesicles. Fe(2+) transport was stimulated by an inwardly directed electrochemical proton gradient across right-side-out vesicles, an effect that was diminished by the addition of valinomycin in the presence of K(+). Fe(2+) transport was inhibited by Zn(2+), in a competitive manner, as well as by Cu(2+) and Mn(2+). These results indicate that inward-directed Fe(2+) transport across the chloroplast inner envelope occurs by a potential-stimulated uniport mechanism.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218-2685, USA. shingles@jhu.edu
authors.forename: Richard
authors.initials: R
authors.lastname: Shingles
authors.forename: Marisa
authors.initials: M
authors.lastname: North
authors.forename: Richard E
authors.initials: RE
authors.lastname: McCarty
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002104:Cadmium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002736:Chloroplasts / Q000502:physiology*; D003300:Copper / Q000494:pharmacology; D005296:Ferrous Compounds / Q000378:metabolism* / Q000494:pharmacology; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000187:drug effects; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D009930:Organic Chemicals; D018532:Pisum sativum / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014634:Valinomycin / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
chemical_list: D005296:Ferrous Compounds; D005456:Fluorescent Dyes; D009930:Organic Chemicals; C431805:Phen Green SK; D002104:Cadmium; D014634:Valinomycin; D008345:Manganese; D003300:Copper; D015032:Zinc; D011188:Potassium