Evidence for the importance of electrostatics in the function of two distinct families of ribosome inactivating toxins
Evidence for the importance of electrostatics in the function of two distinct families of ribosome inactivating toxins
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DOI：
10.1261/rna.619707
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发表时间：
2007-09-01
期刊：
影响因子：
4.5
通讯作者：
Piccirilli, Joseph A.
中科院分区：
文献类型：
--
作者：
Korennykh, Alexei V.;Correll, Carl C.;Piccirilli, Joseph A.
α-肌毒蛋白和蓖麻毒蛋白代表两个结构和机制不同的位点特异性酶家族，其通过不可逆地修饰23 S-28 S rRNA的肌毒蛋白/蓖麻毒蛋白环（SRL）来阻断翻译。α-肌氨酸家族酶被称为核糖毒素并作为核酸内切酶。蓖麻毒素家族酶被命名为核糖体失活蛋白（RIP），并作为N-糖苷酶。最近，我们证明了限制性内切酶的核糖体表面碱性残基可以促进这种核酸内切酶快速而特异地靶向核糖体。在这里，我们报告了三种RIP：蓖麻毒素A，皂草素和gypsophilin以强盐敏感性脱嘌呤核糖体，并达到异常快的k（cat）/K-m，类似于10（9）-10（10）M-1 s（-1），这意味着RIP与核糖毒素共享静电促进核糖体靶向的共同机制。RIP的生物信息学分析表明，表面电荷特性与RIP分子中的运输链的存在相关，这表明RIP运输中的表面电荷的第二个作用。这些发现提出了表面静电作为RIP活动的一个重要决定因素。
alpha-Sarcin and ricin represent two structurally and mechanistically distinct families of site-specific enzymes that block translation by irreversibly modifying the sarcin/ricin loop (SRL) of 23S-28S rRNA. alpha-Sarcin family enzymes are designated as ribotoxins and act as endonucleases. Ricin family enzymes are designated as ribosome inactivating proteins ( RIP) and act as N-glycosidases. Recently, we demonstrated that basic surface residues of the ribotoxin restrictocin promote rapid and specific ribosome targeting by this endonuclease. Here, we report that three RIP: ricin A, saporin, and gypsophilin depurinate the ribosome with strong salt sensitivity and achieve unusually fast k(cat)/K-m similar to 10(9)-10(10) M-1 s(-1), implying that RIP share with ribotoxins a common mechanism of electrostatically facilitated ribosome targeting. Bioinformatics analysis of RIP revealed that surface charge properties correlate with the presence of the transport chain in the RIP molecule, suggesting a second role for the surface charge in RIP transport. These findings put forward surface electrostatics as an important determinant of RIP activity.