Takagi T, Taylor G S, Kusakabe T, Charbonneau H, Buratowski S
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 1998 Aug 18;95(17):9808-12. doi: 10.1073/pnas.95.17.9808.
The superfamily of protein tyrosine phosphatases (PTPs) includes at least one enzyme with an RNA substrate. We recently showed that the RNA triphosphatase domain of the Caenorhabditis elegans mRNA capping enzyme is related to the PTP enzyme family by sequence similarity and mechanism. The PTP most similar in sequence to the capping enzyme triphosphatase is BVP, a dual-specificity PTP encoded by the Autographa californica nuclear polyhedrosis virus. Although BVP previously has been shown to have modest tyrosine and serine/threonine phosphatase activity, we find that it is much more potent as an RNA 5'-phosphatase. BVP sequentially removes gamma and beta phosphates from the 5' end of triphosphate-terminated RNA, leaving a 5'-monophosphate end. The activity was specific for polynucleotides; nucleotide triphosphates were not hydrolyzed. A mutant protein in which the active site cysteine was replaced with serine was inactive. Three other dual-specificity PTPs (VH1, VHR, and Cdc14) did not exhibit detectable RNA phosphatase activity. Therefore, capping enzyme and BVP are members of a distinct PTP-like subfamily that can remove phosphates from RNA.
蛋白质酪氨酸磷酸酶（PTP）超家族中至少包含一种作用于RNA底物的酶。我们最近发现，秀丽隐杆线虫mRNA加帽酶的RNA三磷酸酶结构域在序列相似性和作用机制方面与PTP酶家族相关。在序列上与加帽酶三磷酸酶最相似的PTP是BVP，它是一种由苜蓿银纹夜蛾核型多角体病毒编码的双特异性PTP。尽管之前已证明BVP具有适度的酪氨酸和丝氨酸/苏氨酸磷酸酶活性，但我们发现它作为RNA 5'-磷酸酶的活性要强得多。BVP能依次从三磷酸末端RNA的5'端去除γ和β磷酸基团，留下5'-单磷酸末端。该活性对多核苷酸具有特异性；三磷酸核苷酸不会被水解。活性位点半胱氨酸被丝氨酸取代的突变蛋白没有活性。其他三种双特异性PTP（VH1、VHR和Cdc14）未表现出可检测到的RNA磷酸酶活性。因此，加帽酶和BVP是一个独特的类PTP亚家族的成员，该亚家族能够从RNA上去除磷酸基团。
