Alphaherpesviral ribonucleotide reductase (RNR) is composed of large (pUL39, RR1) and small (pUL40, RR2) subunits. This enzyme can catalyze conversion of ribonucleotide to deoxynucleotide diphosphates that are further phosphorylated into deoxynucleotide triphosphate (dNTPs). The dNTPs are substrates for de novo viral DNA synthesis in infected host cells. The enzymatic activity of RNR depends on association between RR1 and RR2. However, the molecular basis underlying alphaherpesviral RNR complex formation is still largely unknown. In the current study, we investigated the pseudorabies virus (PRV) RNR interaction domains in pUL39 and pUL40. The interaction of pUL39 and pUL40 was identified by co-immunoprecipitation (co-IP) and colocalization analyses. Furthermore, the interaction amino acid (aa) domains in pUL39 and pUL40 were mapped using a series of truncated proteins. Consequently, the 90―210 aa in pUL39 was identified to be responsible for the interaction with pUL40. In turn, the 66―152, 218―258 and 280―303 aa in pUL40 could interact with pUL39, respectively. Deletion of 90―210 aa in pUL39 completely abrogated the interaction with pUL40. Deletion of 66―152, 218―258 and 280―303 aa in pUL40 remarkably weakened the interaction with pUL39, whereas a weak interaction could still be observed. Amino acid sequence alignments showed that the interaction domains identified in PRV pUL39/pUL40 were relatively non-conserved among the selected RNR subunits in alphaherpesviruses HSV1, HSV2, HHV3(VZV), BHV1, EHV1 and DEV. However, they were relatively conserved among PRV, HSV1 and HSV2. Collectively, our findings provided some molecular targets for inhibition of pUL39―pUL40 interaction to antagonize viral replication in PRV infected hosts.

甲型疱疹病毒核糖核苷酸还原酶（RNR）由大（pUL39，RR1）和小（pUL40，RR2）亚基组成。该酶可以催化核糖核苷酸向脱氧核苷酸二磷酸的转化，该磷酸进一步被磷酸化为脱氧核苷酸三磷酸（dNTP）。dNTP是从头开始的底物感染宿主细胞中的病毒DNA合成。RNR的酶活性取决于RR1和RR2之间的关联。但是，α疱疹病毒RNR复合物形成的分子基础仍然是未知的。在当前的研究中，我们调查了pUL39和pUL40中的伪狂犬病病毒（PRV）RNR相互作用域。通过共免疫沉淀（co-IP）和共定位分析鉴定了pUL39和pUL40的相互作用。此外，使用一系列截短的蛋白定位了pUL39和pUL40中的相互作用氨基酸（aa）结构域。因此，pUL39中的90-210aa被认为是与pUL40相互作用的原因。反过来，pUL40中的66-152、218-258和280-303aa可能分别与pUL39相互作用。pUL39中90〜210aa的缺失完全消除了与pUL40的相互作用。pUL40中66-152、218-258和280-303aa的缺失显着减弱了与pUL39的相互作用，但仍然观察到弱相互作用。氨基酸序列比对显示，在丙型疱疹病毒HSV1，HSV2，HHV3（VZV），BHV1，EHV1和DEV的选定RNR亚基中，在PRV pUL39 / pUL40中鉴定的相互作用结构域相对不保守。但是，它们在PRV，HSV1和HSV2中相对保守。总的来说，我们的发现为抑制pUL39-pUL40相互作用提供了一些分子靶标，以拮抗PRV感染宿主中的病毒复制。氨基酸序列比对显示，在丙型疱疹病毒HSV1，HSV2，HHV3（VZV），BHV1，EHV1和DEV的选定RNR亚基中，在PRV pUL39 / pUL40中鉴定的相互作用结构域相对不保守。但是，它们在PRV，HSV1和HSV2中相对保守。总的来说，我们的发现为抑制pUL39-pUL40相互作用提供了一些分子靶标，以拮抗PRV感染宿主中的病毒复制。氨基酸序列比对显示，在丙型疱疹病毒HSV1，HSV2，HHV3（VZV），BHV1，EHV1和DEV的选定RNR亚基中，在PRV pUL39 / pUL40中鉴定的相互作用结构域相对不保守。但是，它们在PRV，HSV1和HSV2中相对保守。总的来说，我们的发现为抑制pUL39-pUL40相互作用提供了一些分子靶标，以拮抗PRV感染宿主中的病毒复制。