Effects of cytoplasmic Mg2+ on slowly activating channels in isolated vacuoles of Beta vulgaris

被引:56
作者
Carpaneto, A [1 ]
Cantù, AM [1 ]
Gambale, F [1 ]
机构
[1] CNR, Ist Cibernet & Biofis, I-16149 Genoa, Italy
关键词
Beta vulgaris; divalent ions; ion channel; vacuole; tonoplast;
D O I
10.1007/s004250100519
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
The slow vacuolar (SV) channel can mediate a large part of the ionic current in plant tonoplasts, but its actual physiological role is still unclear. We demonstrate that in vacuoles from the taproots of sugar beet (Beta vulgaris L.), besides Ca2+, cytoplasmic Mg2+ also plays an important role in promoting the activation of the SV channel. An increase in Mg2+ concentration decreases the time constants of channel activation and deactivation, and determines a consistent shift, towards negative voltages, of the conductance characteristic; as an example, when the free concentration of Mg2+ was increased from the micromolar range up to 10 mM the activation shifted by about -60 mV. The experimental results obtained, which are based on a fast perfusion procedure allowing us to change the solution bathing the vacuole in a few milliseconds, suggest that magnesium-binding is a faster process than the voltage-activation gating of the channel, which constitutes the rate-limiting step controlling channel opening. Interestingly, the activation of the channel mediated by Mg2+ depends on the cooperative binding of at least three magnesium ions. We verified that cytoplasmic magnesium favours the activation of SV channels in the presence of nanomolar cytoplasmic calcium concentrations. A critical discussion on the Calcium Induced Calcium Release (CICR) mechanism proposed for the SV channel is presented.
引用
收藏
页码:457 / 468
页数:12
相关论文
共 39 条
[21]   CYTOPLASMIC CALCIUM REGULATES VOLTAGE-DEPENDENT ION CHANNELS IN PLANT VACUOLES [J].
HEDRICH, R ;
NEHER, E .
NATURE, 1987, 329 (6142) :833-836
[22]   CHARACTERIZATION OF AN ANION-PERMEABLE CHANNEL FROM SUGAR-BEET VACUOLES - EFFECT OF INHIBITORS [J].
HEDRICH, R ;
KURKDJIAN, A .
EMBO JOURNAL, 1988, 7 (12) :3661-3666
[23]   NEGATIVE SURFACE CHARGE NEAR SODIUM CHANNELS OF NERVE - DIVALENT IONS, MONOVALENT IONS, AND PH [J].
HILLE, B ;
WOODHULL, AM ;
SHAPIRO, BI .
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, 1975, 270 (908) :301-318
[24]  
Hille B., 1992, IONIC CHANNELS EXCIT
[25]   MODULATION OF CALCIUM-ACTIVATED NONSELECTIVE CATION CHANNEL ACTIVITY BY NITRIC-OXIDE IN RAT BROWN ADIPOSE-TISSUE [J].
KOIVISTO, A ;
NEDERGAARD, J .
JOURNAL OF PHYSIOLOGY-LONDON, 1995, 486 (01) :59-65
[26]   CYCLIC NUCLEOTIDE-GATED CHANNELS OF RAT OLFACTORY RECEPTOR-CELLS - DIVALENT-CATIONS CONTROL THE SENSITIVITY TO CAMP [J].
LYNCH, JW ;
LINDEMANN, B .
JOURNAL OF GENERAL PHYSIOLOGY, 1994, 103 (01) :87-106
[27]   ON NATURE OF ALLOSTERIC TRANSITIONS - A PLAUSIBLE MODEL [J].
MONOD, J ;
WYMAN, J ;
CHANGEUX, JP .
JOURNAL OF MOLECULAR BIOLOGY, 1965, 12 (01) :88-&
[28]   Effective gating charges per channel in voltage-dependent K+ and Ca2+ channels [J].
Noceti, F ;
Baldelli, P ;
Wei, XY ;
Qin, N ;
Toro, L ;
Birnbaumer, L ;
Stefani, E .
JOURNAL OF GENERAL PHYSIOLOGY, 1996, 108 (03) :143-155
[29]   Magnesium sensitizes slow vacuolar channels to physiological cytosolic calcium and inhibits fast vacuolar channels in fava bean guard cell vacuoles [J].
Pei, ZM ;
Ward, JM ;
Schroeder, JI .
PLANT PHYSIOLOGY, 1999, 121 (03) :977-986
[30]   THE PERMEABILITY OF THE CGMP-ACTIVATED CHANNEL TO ORGANIC CATIONS IN RETINAL RODS OF THE TIGER SALAMANDER [J].
PICCO, C ;
MENINI, A .
JOURNAL OF PHYSIOLOGY-LONDON, 1993, 460 :741-758