Transport kinetics, cation inhibition and intracellular location of accumulated caesium in the green microalga Chlorella salina
Transport kinetics, cation inhibition and intracellular location of accumulated caesium in the green microalga Chlorella salina
复制标题
绿色微藻小球藻中积累的铯的运输动力学、阳离子抑制和细胞内定位
DOI：
10.1099/00221287-139-4-827
复制
发表时间：
1993
期刊：
影响因子：
1.5
通讯作者：
G. Gadd
中科院分区：
文献类型：
--
作者：
S. Avery;G. Codd;G. Gadd
总结：在添加50 μM-CsCl和137 Cs的缓冲液（pH 8.0）中，小球藻对铯的积累可持续约15 h，并呈现一级动力学，表明其为单一的限速转运过程。流出的Cs+从Cs+负载细胞发生在两个不同的阶段：一个快速的初始损失，约占11%的总细胞Cs+，对应于从细胞表面释放，而第二，较慢，流出相对应的损失从细胞质和空泡。亚细胞Cs ~+区室化分析表明，大部分Cs ~+聚集在C.盐藻，少量与细胞表面相关或位于细胞质中。Cs+进入液泡的吸收与K+的化学计量交换相关。然而，没有损失的K+从细胞表面或细胞质是明显的，也不是Cs+或K+与不溶性细胞内成分。Cs+跨液泡膜通量的计算值约等于或高于总细胞流入的值。Cs ~+内流在较低的Cs ~+浓度范围内（0.01-0.25 mM）服从Michaelis-Menten动力学，
m ± 0.5 mM是明显的。其它一价阳离子对Cs+内流的影响表明K+和Rb+是竞争性的，NH+对Cs+内流的影响不明显。
4种Cs+摄取的非竞争性/非竞争性抑制剂。抑制作用大小顺序为Rb+ > K+ > NH+
4.我们提出，一个单一的，相对非选择性的，限速运输系统的Cs+内流位于细胞质膜上。盐藻的液泡膜具有较强的渗透性，有利于Cs+向液泡的转运。
Summary: Caesium accumulation by Chlorella salina, from buffer (pH 8.0) supplemented with 50 μM-CsCl and 137Cs, continued for approximately 15 h and displayed first-order kinetics, indicating a single rate-limiting transport process. Efflux of Cs+ from Cs+-loaded cells occurred in two distinct phases: a rapid initial loss, representing approximately 11% of total cellular Cs+, corresponded to release from the cell surface, whereas a second, slower, phase of efflux corresponded to loss from the cytoplasm and vacuole. Analysis of subcellular Cs+ compartmentation revealed that most Cs+ was accumulated into the vacuole of C. salina, with lesser amounts being associated with the cell surface or located in the cytoplasm. Uptake of Cs+ into the vacuole was correlated with a stoichiometric exchange for K+. However, no loss of K+ from the cell surface or cytoplasm was evident nor was Cs+ or K+ associated with insoluble intracellular components. Calculated values for the Cs+ flux across the vacuolar membrane were approximately equal to, or higher than, values for total cellular influx. Cs+ influx obeyed Michaelis–Menten kinetics over the lower range of external Cs+ concentrations examined (0.01–0.25 mM) and a single transport system with a K
m ± 0.5 mM was evident. The effects of other monovalent cations on Cs+ influx implied that K+ and Rb+ were competitive, and NH+
4 non-competitive/uncompetitive inhibitors of Cs+ uptake. The order of inhibition was Rb+ > K+ > NH+
4. We propose that a single, relatively non-selective, rate-limiting transport system for Cs+ influx is located on the cytoplasmic membrane of C. salina, while a more permeable vacuolar membrane facilitates transport of Cs+ into the vacuole.