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Concanamycin 4‐B: A Potent Inhibitor of Vacuolar pH Regulation in Chara Cells
Author(s) -
Tazawa M.,
Okazaki Y.,
Moriyama Y.,
Iwasaki N.
Publication year - 1995
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1995.tb00833.x
Subject(s) - bafilomycin , vacuole , chara , chemistry , atpase , proton transport , chloramphenicol , biochemistry , membrane , biology , enzyme , botany , cytoplasm , antibiotics , apoptosis , autophagy
Concanamycin 4‐B, a macrolide antibiotic with an 18‐membered lactone ring, is known as a specific inhibitor of the vacuolar type of H + ‐ATPase, as is bafilomycin A 1 . The drug was tested for its effect on regulation of the vacuolar pH (pH v ) of internodal cells of a fresh water characean alga, Chara corallina , under normal conditions and under salt stress. The pH v was measured either on isolated vacuolar sap with a conventional pH electrode or directly by inserting a pH‐sensitive glass microelectrode into the vacuole. Proton‐pumping into tonoplast vesicles was almost completely inhibited by concanamycin 4‐B at 1 nM. Concanamycin 4‐B at 1 μM significantly increased pH v while bafilomycin A 1 was ineffective when applied at 1 μM. Concanamycin 4‐B did not affect pH v when applied at 0.1 μM and increasing the concentration to 10 μM did not amplify the degree of alkalization. Concanamycin 4‐B also inhibited pH v regulation under NaCl stress. When Chara cells were treated with 100 mM NaCl, pH v promptly increased and then recovered to the original level. The reacidification was completely inhibited by concanamycin 4‐B (1 μM), suggesting that the reacidification was achieved by the H + ‐ATPase of the tonoplast.