RRC ID 27850
著者 Araie H, Sakamoto K, Suzuki I, Shiraiwa Y.
タイトル Characterization of the selenite uptake mechanism in the coccolithophore Emiliania huxleyi (Haptophyta).
ジャーナル Plant Cell Physiol
Abstract The marine coccolithophore Emiliania huxleyi (Haptophyta) requires selenium as an essential element for growth, and the active species absorbed is selenite, not selenate. This study characterized the selenite uptake mechanism using ⁷⁵Se as a tracer. Kinetic analysis of selenite uptake showed the involvement of both active and passive transport processes. The active transport was suppressed by 0.5 mM vanadate, a membrane-permeable inhibitor of H⁺-ATPase, at pH 8.3. When the pH was lowered from 8.3 to 5.3, the selenite uptake activity greatly increased, even in the presence of vanadate, suggesting that the H⁺ concentration gradient may be a motive force for selenite transport. [⁷⁵Se]Selenite uptake at selenite-limiting concentrations was hardly affected by selenate, sulfate and sulfite, even at 100 μM. In contrast, 3 μM orthophosphate increased the K(m) 5-fold. These data showed that HSeO₃⁻, a dominant selenite species at acidic pH, is the active species for transport through the plasma membrane and transport is driven by ΔpH energized by H⁺-ATPase. Kinetic analysis showed that the selenite uptake activity was competitively inhibited by orthophosphate. Furthermore, the active selenite transport mechanism was shown to be induced de novo under Se-deficient conditions and induction was suppressed by the addition of either sufficient selenite or cycloheximide, an inhibitor of de novo protein synthesis. These results indicate that E. huxleyi cells developed an active selenite uptake mechanism to overcome the disadvantages of Se limitation in ecosystems, maintaining selenium metabolism and selenoproteins for high viability.
巻・号 52(7)
ページ 1204-10
公開日 2011-7-1
DOI 10.1093/pcp/pcr070
PII pcr070
PMID 21632656
MeSH Biological Transport, Active Haptophyta / metabolism* Hydrogen-Ion Concentration Proton-Translocating ATPases / antagonists & inhibitors Proton-Translocating ATPases / metabolism Selenic Acid Selenium Compounds / metabolism Sodium Selenite / pharmacokinetics* Sulfites / metabolism Vanadates / pharmacology
IF 4.062
引用数 21
WOS 分野 PLANT SCIENCES CELL BIOLOGY
リソース情報
藻類 NIES-837