Evidence for two distinct intracellular pools of inorganic sulfate in Penicillium notatum.
Evidence for two distinct intracellular pools of inorganic sulfate in Penicillium notatum.
复制标题
青霉中存在两种不同的细胞内无机硫酸盐库的证据。
DOI：
10.1128/jb.162.3.881-887.1985
复制
发表时间：
1985
影响因子：
3.2
通讯作者：
Segel,IH
中科院分区：
文献类型：
--
作者：
Hunter,DR;Segel,IH
一株不能代谢无机硫酸盐的新青霉菌株可以在内部积累硫酸盐，达到比培养基中剩余硫酸盐高出10(5)的表观平衡浓度。在所有初始外部硫酸盐浓度低于最终超过电池内部容量的浓度时，表观Keq几乎是恒定的。在零净通量的平衡条件下，外部的35SO42-与内部的未标记的SO42-以与硫酸盐运输系统的动力学常数一致的速率交换。外排实验表明，硫酸盐占据了两个不同的胞内池。当预加载细胞的悬浮液在pH为8.4时调节到10 mM叠氮(t 1/2，0.38分钟)时，池1的特征是35SO42-的快速释放。池1中的35SO42-还与未标记的介质硫酸盐快速交换。在pH为8.4时，叠氮化物或未标记硫酸盐(t1/2，32~49min)诱导35SO42-的缓慢释放。在35SO42-积累过程的早期，高达78%的底物被输送到池1中。在平衡时，池1仅占总积累的35SO42-的2%左右。35SO42-的积累动力学符合下列顺序过程：中等-池1-池2。莫能菌素(33微米)加速35SO42-从池1到池2的转移。瓦林霉素(0.2微米)和四苯基硼(1 MM)延缓35SO42-从池1到池2的转移。在所用浓度下，离子载体和四苯硼都不影响35SO42-的总吸收。池2可能存在于液泡或其他细胞内细胞器中。提出了硫酸盐从1号池向2号池迁移的模型。
A strain of Penicillium notatum unable to metabolize inorganic sulfate can accumulate sulfate internally to an apparent equilibrium concentration 10(5) greater than that remaining in the medium. The apparent Keq is near constant at all initial external sulfate concentrations below that which would eventually exceed the internal capacity of the cells. Under equilibrium conditions of zero net flux, external 35SO42- exchanges with internal, unlabeled SO42- at a rate consistent with the kinetic constants with the sulfate transport system. Efflux experiments demonstrated that sulfate occupies two distinct intracellular pools. Pool 1 is characterized by the rapid release of 35SO42- when the suspension of preloaded cells is adjusted to 10 mM azide at pH 8.4 (t 1/2, 0.38 min). 35SO42- in pool 1 also rapidly exchanges with unlabeled medium sulfate. Pool 2 is characterized by the slow release of 35SO42- induced by azide at pH 8.4 or unlabeled sulfate (t 1/2, 32 to 49 min). Early in the 35SO42- accumulation process, up to 78% of the total transported substrate is found in pool 1. At equilibrium, pool 1 accounts for only about 2% of the total accumulated 35SO42-. The kinetics of 35SO42- accumulation is consistent with the following sequential process: medium----pool 1----pool 2. Monensin (33 microns) accelerates the transfer of 35SO42- from pool 1 to pool 2. Valinomycin (0.2 microM) and tetraphenylboron- (1 mM) retard the transfer of 35SO42- from pool 1 to pool 2. At the concentrations used, neither of the ionophores nor tetraphenylboron- affect total 35SO42- uptake. Pool 2 may reside in a vacuole or other intracellular organelle. A model for the transfer of sulfate from pool 1 to pool 2 is presented.