Versaw W K, Metzenberg R L
Department of Biomolecular Chemistry, University of Wisconsin, Madison 53706, USA.
Proc Natl Acad Sci U S A. 1995 Apr 25;92(9):3884-7. doi: 10.1073/pnas.92.9.3884.
The filamentous fungus Neurospora crassa possesses two nonhomologous high-affinity phosphate permeases, PHO-4 and PHO-5. We have isolated separate null mutants of these permeases, allowing us to study the remaining active transporter in vivo in terms of phosphate uptake and sensitivity to inhibitors. The specificity for the cotransported cation differs for PHO-4 and PHO-5, suggesting that these permeases employ different mechanisms for phosphate translocation. Phosphate uptake by PHO-4 is stimulated 85-fold by the addition of Na+, which supports the idea that PHO-4 is a Na(+)-phosphate symporter. PHO-5 is unaffected by Na+ concentration but is much more sensitive to elevated pH than is PHO-4. Presumably, PHO-5 is a H(+)-phosphate symporter. Na(+)-coupled symport is usually associated with animal cells. The finding of such a system in a filamentous fungus is in harmony with the idea that the fungal and animal kingdoms are more closely related to each other than either is to the plant kingdom.
丝状真菌粗糙脉孢菌拥有两种非同源的高亲和力磷酸盐转运蛋白，即PHO - 4和PHO - 5。我们已经分离出了这些转运蛋白各自的无效突变体，这使我们能够在体内研究剩余的活性转运蛋白在磷酸盐摄取和对抑制剂敏感性方面的情况。PHO - 4和PHO - 5对共转运阳离子的特异性不同，这表明这些转运蛋白采用不同的机制进行磷酸盐转运。通过添加Na⁺，PHO - 4的磷酸盐摄取受到85倍的刺激，这支持了PHO - 4是一种Na⁺-磷酸盐同向转运体的观点。PHO - 5不受Na⁺浓度的影响，但比PHO - 4对升高的pH更敏感。据推测，PHO - 5是一种H⁺-磷酸盐同向转运体。Na⁺偶联的同向转运通常与动物细胞相关。在丝状真菌中发现这样一个系统与真菌界和动物界彼此之间的关系比它们与植物界的关系更密切这一观点是一致的。
