Outten C E, O'Halloran T V
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
Science. 2001 Jun 29;292(5526):2488-92. doi: 10.1126/science.1060331. Epub 2001 Jun 7.
Intracellular zinc is thought to be available in a cytosolic pool of free or loosely bound Zn(II) ions in the micromolar to picomolar range. To test this, we determined the mechanism of zinc sensors that control metal uptake or export in Escherichia coli and calibrated their response against the thermodynamically defined free zinc concentration. Whereas the cellular zinc quota is millimolar, free Zn(II) concentrations that trigger transcription of zinc uptake or efflux machinery are femtomolar, or six orders of magnitude less than one atom per cell. This is not consistent with a cytosolic pool of free Zn(II) and suggests an extraordinary intracellular zinc-binding capacity. Thus, cells exert tight control over cytosolic metal concentrations, even for relatively low-toxicity metals such as zinc.
细胞内锌被认为以微摩尔到皮摩尔范围内游离或松散结合的Zn(II)离子的胞质池形式存在。为了验证这一点,我们确定了控制大肠杆菌中金属摄取或输出的锌传感器机制,并根据热力学定义的游离锌浓度校准了它们的响应。虽然细胞内锌配额为毫摩尔,但触发锌摄取或外排机制转录的游离Zn(II)浓度为飞摩尔,即比每个细胞一个原子少六个数量级。这与游离Zn(II)的胞质池不一致,表明细胞内具有非凡的锌结合能力。因此,即使对于毒性相对较低的金属如锌,细胞也能严格控制胞质金属浓度。