Coburn J, Kane A V, Feig L, Gill D M
Center for Gastroenterology Research on Absorptive and Secretory Processes, New England Medical Center, Boston, Massachusetts 02111.
J Biol Chem. 1991 Apr 5;266(10):6438-46.
Pseudomonas aeruginosa exoenzyme S ADP-ribosylates several GTP-binding proteins of apparent Mr = 23,000-25,000. Exoenzyme S absolutely requires a soluble eukaryotic protein, which we have named FAS (Factor Activating exoenzyme S), in order to ADP-ribosylate all substrates. The rate of ADP-ribosylation of all exoenzyme S substrates increases linearly with time and with the FAS concentration. FAS is wide-spread in eukaryotes but appears to be absent from prokaryotes. We have estimated the molecular mass of the protein to be approximately 29,000 daltons and its pI to be 4.3-4.5. Several bacterial toxins share this sort of requirement for the presence of a eukaryotic protein for enzymic activity. In particular, FAS resembles ADP-ribosylation factor, a 21,000-dalton GTP-binding protein which performs an analogous function for cholera toxin. However, we can find no evidence that FAS binds GTP. In the presence of FAS, exoenzyme S ADP-ribosylates several proteins in lysates of P. aeruginosa. The requirement for a eukaryotic protein for enzymic activity, which is common to several bacterial toxins, may be a device to identify the eukaryotic environment and to ensure that the enzymes cannot function within and harm the toxin-producing bacteria.
铜绿假单胞菌外毒素S能对几种表观分子量为23,000 - 25,000的GTP结合蛋白进行ADP核糖基化。外毒素S绝对需要一种可溶性真核蛋白（我们将其命名为FAS，即激活外毒素S的因子）才能对所有底物进行ADP核糖基化。所有外毒素S底物的ADP核糖基化速率随时间和FAS浓度呈线性增加。FAS在真核生物中广泛存在，但在原核生物中似乎不存在。我们估计该蛋白的分子量约为29,000道尔顿，其pI为4.3 - 4.5。几种细菌毒素都有这种对真核蛋白存在以实现酶活性的需求。特别是，FAS类似于ADP核糖基化因子，一种21,000道尔顿的GTP结合蛋白，它对霍乱毒素发挥类似的功能。然而，我们没有发现FAS结合GTP的证据。在FAS存在的情况下，外毒素S能对铜绿假单胞菌裂解物中的几种蛋白进行ADP核糖基化。几种细菌毒素共有的对真核蛋白以实现酶活性的需求，可能是一种识别真核环境并确保这些酶不会在产生毒素的细菌内发挥作用并造成损害的机制。
