通過(guò)三張丙型肝炎病毒(HCV)動(dòng)力蛋白及其底物的構(gòu)象快照，美國(guó)洛克菲勒大學(xué)的研究人員首次提供了HCV NS3解旋酶沿著核酸鏈單向移動(dòng)的證據(jù),，這項(xiàng)研究或許有助于藥物設(shè)計(jì)者根據(jù)這一特點(diǎn)設(shè)計(jì)出阻斷該病毒復(fù)制的藥物,。
研究人員在之前的研究中已經(jīng)了解到HCV NS3解旋酶的運(yùn)動(dòng)需要ATP提供能量支持,，而且科學(xué)家也獲得了NS3的晶體結(jié)構(gòu)。據(jù)最近的一項(xiàng)發(fā)表于Proceedings of the National Academy of Sciences的研究報(bào)告,，Charles M. Rice等人研究顯示了ATP如何連續(xù)地改造DNA和NS3解旋酶之間的聯(lián)系,，并找到在解旋酶移動(dòng)過(guò)程中起關(guān)鍵作用的因素,。
據(jù)研究人員Gu介紹，當(dāng)ATP與NS3結(jié)合以及ATP發(fā)生水解時(shí),，NS3和DNA會(huì)發(fā)生一系列的重要轉(zhuǎn)變,，如果在轉(zhuǎn)變過(guò)程中，抑制參與該過(guò)程中的某些蛋白,，那么將會(huì)抑制解旋酶的運(yùn)動(dòng)并使病毒復(fù)制終止,。
通過(guò)分子快照，研究人員詳細(xì)描述了NS3如何沿著核酸底物運(yùn)動(dòng)的過(guò)程,。當(dāng)NS3與核酸相結(jié)合時(shí),，NS3的形狀類(lèi)似于希臘字母“λ”。在NS3沿核酸底物單向運(yùn)動(dòng)的過(guò)程中關(guān)鍵的一點(diǎn)是需要一個(gè)磷酸基團(tuán)的參與,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS December 31, 2009, doi: 10.1073/pnas.0913380107
Three conformational snapshots of the hepatitis C virus NS3 helicase reveal a ratchet translocation mechanism
Meigang Gu1 and Charles M. Rice1
Center for the Study of Hepatitis C, Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY 10065
A virally encoded superfamily-2 (SF2) helicase (NS3h) is essential for the replication of hepatitis C virus, a leading cause of liver disease worldwide. Efforts to elucidate the function of NS3h and to develop inhibitors against it, however, have been hampered by limited understanding of its molecular mechanism. Here we show x-ray crystal structures for a set of NS3h complexes, including ground-state and transition-state ternary complexes captured with ATP mimics (ADP·BeF3 and ). These structures provide, for the first time, three conformational snapshots demonstrating the molecular basis of action for a SF2 helicase. Upon nucleotide binding, overall domain rotation along with structural transitions in motif V and the bound DNA leads to the release of one base from the substrate base-stacking row and the loss of several interactions between NS3h and the 3′ DNA segment. As nucleotide hydrolysis proceeds into the transition state, stretching of a “spring” helix and another overall conformational change couples rearrangement of the (d)NTPase active site to additional hydrogen-bonding between NS3h and DNA. Together with biochemistry, these results demonstrate a “ratchet” mechanism involved in the unidirectional translocation and define the step size of NS3h as one base per nucleotide hydrolysis cycle. These findings suggest feasible strategies for developing specific inhibitors to block the action of this attractive, yet largely unexplored drug target.
