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Magnesium-dependent interaction of PKR with adenovirus VAI.

机译:PKR与腺病毒VAI的镁依赖性相互作用。

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Protein kinase R (PKR) is an interferon-induced kinase that plays a pivotal role in the innate immunity pathway for defense against viral infection. PKR is activated to undergo autophosphorylation upon binding to RNAs that contain duplex regions. Activated PKR phosphorylates the alpha-subunit of eukaryotic initiation factor 2, thereby inhibiting protein synthesis in virus-infected cells. Viruses have evolved diverse PKR-inhibitory strategies to evade the antiviral response. Adenovirus encodes virus-associated RNA I (VAI), a highly structured RNA inhibitor that binds PKR but fails to activate. We have characterized the stoichiometry and affinity of PKR binding to define the mechanism of PKR inhibition by VAI. Sedimentation velocity and isothermal titration calorimetry measurements indicate that PKR interactions with VAI are modulated by Mg(2+). Two PKR monomers bind in the absence of Mg(2+), but a single monomer binds in the presence of divalent ion. Known RNA activators of PKR are capable of binding multiple PKR monomers to allow the kinase domains to come into close proximity and thus enhance dimerization. We propose that VAI acts as an inhibitor of PKR because it binds and sequesters a single PKR in the presence of divalent cation.
机译:蛋白激酶R(PKR)是干扰素诱导的激酶,在天然免疫途径中起着关键作用,可防御病毒感染。与包含双链体区域的RNA结合后,PKR被激活以进行自磷酸化。激活的PKR使真核生物起始因子2的α亚基磷酸化,从而抑制病毒感染细胞中的蛋白质合成。病毒已经进化出多种PKR抑制策略来逃避抗病毒反应。腺病毒编码病毒相关的RNA I(VAI),RNA I是一种高度结构化的RNA抑制剂,与PKR结合但无法激活。我们已经表征了PKR结合的化学计量和亲和力,以定义VAI抑制PKR的机制。沉降速度和等温滴定量热法测量表明,与VAI的PKR相互作用受Mg(2+)调节。在不存在Mg(2+)的情况下,两个PKR单体结合,但是在存在二价离子的情况下,一个单体结合。已知的PKR RNA激活剂能够结合多个PKR单体,从而使激酶结构域紧密接近,从而增强二聚作用。我们建议VAI充当PKR抑制剂,因为它在二价阳离子存在下结合并隔离单个PKR。

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