Basic amino acids and inorganic polyphosphates in Neurospora crassa: independent regulation of vacuolar pools
Basic amino acids and inorganic polyphosphates in Neurospora crassa: independent regulation of vacuolar pools
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粗糙脉孢菌中的碱性氨基酸和无机多磷酸盐：液泡池的独立调节
作者：
C. Cramer;L. E. Vaughn;R. Davis
至少78%，也许所有的无机多磷酸盐被证明是包含在囊泡（液泡）的粗糙脉孢菌，其中超过97%的可溶性精氨酸，赖氨酸和鸟氨酸池是已知的积累。此外，合成的多磷酸盐可以在平衡透析中从稀溶液（0.01 mM）中浓缩精氨酸高达400倍。由于这些原因，并且因为碱性氨基酸和多磷酸盐磷的摩尔比约为1，我们测试了它们之间存在专性生理关系的假设。氮饥饿和精氨酸过量施加在细胞上的实验表明，多磷酸盐含量对碱性氨基酸含量的变化不敏感。涉及磷酸盐饥饿和恢复的实验表明，碱性氨基酸含量几乎完全独立于多磷酸盐池。此外，尽管多磷酸盐耗尽，但囊泡中精氨酸的正常高度区室化仍得以维持，并且精氨酸仍通过囊泡膜进行交换。我们的结论是N. crassa，像酵母一样，可以独立地调节多磷酸盐和碱性氨基酸，并且囊泡中碱性氨基酸的积累除了与多磷酸盐的电荷相互作用外，还可能取决于能量需求机制。
At least 78%, and perhaps all, of inorganic polyphosphate is shown to be contained within the vesicles (vacuoles) of Neurospora crassa, where over 97% of the soluble arginine, lysine, and ornithine pools are known to accumulate. Furthermore, synthetic polyphosphate can concentrate arginine up to 400-fold from dilute (0.01 mM) solutions in equilibrium dialysis. For these reasons and because the molar ratio of basic amino acids and polyphosphate phosphorus is approximately 1, we tested the hypothesis that there was an obligate physiological relationship between them. Experiments in which nitrogen starvation and arginine excess were imposed upon cells showed that polyphosphate content was insensitive to changes in the basic amino acid content. Experiments involving phosphate starvation and restoration showed that basic amino acid content was almost wholly independent of polyphosphate pools. Moreover, the normal high degree of compartmentation of arginine in vesicles was maintained despite polyphosphate depletion, and arginine was still exchanged across the vesicular membrane. We conclude that N. crassa, like yeasts, can regulate polyphosphates and basic amino acids independently, and that the accumulation of basic amino acids in vesicles may depend upon an energy-requiring mechanism in addition to the demonstrated charge interaction with polyphosphate.