Sacco M, Medoff G, Lambowitz A M, Kumar B V, Kobayashi G S, Painter A
J Biol Chem. 1983 Jul 10;258(13):8223-30.
When the mycelial to yeast transition of the dimorphic fungus Histoplasma capsulatum is induced by a temperature shift from 25 to 37 degrees C, the activities of the cytochrome system and the alternate oxidase decrease in parallel over the first 24 to 40 h (stage 1 of the transition). The decrease in activity of the cytochrome system is correlated with extensive decreases in the amounts of cytochromes b, c, and aa3, assayed spectrophotometrically. After 40 h, the cells enter a dormant phase (stage 2 of the transition) and cysteine or other sulfhydryl-containing compounds are required to reactivate mitochondrial respiration. This reactivation is due to the establishment of shunt pathways which bypass blocked segments of the electron transport system. The "shunt" pathways operate normally in mycelia grown at 25 degrees C, but are shut down during the transition, possibly because of depletion of intracellular cysteine. The longstanding observation that cysteine is required to progress beyond the initial stages of the morphological transition may be due, at least in part, to the reactivation of these "shunt" pathways.
当二态真菌荚膜组织胞浆菌的菌丝体向酵母转变通过将温度从25℃转移至37℃诱导时，在最初的24至40小时（转变的第1阶段），细胞色素系统和交替氧化酶的活性平行下降。细胞色素系统活性的下降与通过分光光度法测定的细胞色素b、c和aa3含量的大幅下降相关。40小时后，细胞进入休眠期（转变的第2阶段），需要半胱氨酸或其他含巯基的化合物来重新激活线粒体呼吸。这种重新激活是由于建立了旁路途径，绕过了电子传递系统中受阻的部分。“旁路”途径在25℃生长的菌丝体中正常运作，但在转变过程中关闭，可能是由于细胞内半胱氨酸的消耗。长期以来观察到需要半胱氨酸才能超越形态转变的初始阶段，这可能至少部分归因于这些“旁路”途径的重新激活。
