大肠杆菌的乳糖通透酶：组氨酸-322和谷氨酸-325可能是电荷中继系统的组成部分。
lac permease of Escherichia coli: histidine-322 and glutamic acid-325 may be components of a charge-relay system.
作者信息
Carrasco N, Antes L M, Poonian M S, Kaback H R
出版信息
Biochemistry. 1986 Aug 12;25(16):4486-8. doi: 10.1021/bi00364a004.
When Glu-325 in the lac permease of Escherichia coli is replaced with Ala, lactose/H+ symport is abolished. Thus, the altered permease catalyzes neither uphill lactose accumulation nor efflux. Remarkably, however, permease with Ala-325 catalyzes exchange and counterflow at completely normal rates. Taken together with the results presented in the accompanying paper [Püttner, I. B., Sarkar, H. K., Poonian, M. S., & Kaback, H. R. (1986) Biochemistry (preceding paper in this issue)], the findings suggest that the His-322 and Glu-325 may be components of a charge-relay system that plays an important role in the coupled translocation of lactose and H+.
当大肠杆菌乳糖通透酶中的Glu-325被丙氨酸取代时，乳糖/H⁺同向转运就会被消除。因此，这种改变后的通透酶既不催化乳糖的上坡积累，也不催化其外流。然而，值得注意的是，含有Ala-325的通透酶以完全正常的速率催化交换和逆流。结合随附论文[Püttner, I. B., Sarkar, H. K., Poonian, M. S., & Kaback, H. R. (1986) Biochemistry（本期之前的论文）]中给出的结果，这些发现表明His-322和Glu-325可能是电荷中继系统的组成部分，该系统在乳糖和H⁺的偶联转运中起重要作用。
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