Using coevolution-network interference based on the comparison of two phylogenetically distantly related isolates, one from the main group M and the other from the minor group O of HIV-1, we identify, in the C-terminal domain (CTD) of integrase, a new functional motif constituted by four non-contiguous amino acids (N₂₂₂K₂₄₀N₂₅₄K₂₇₃). Mutating the lysines abolishes integration through decreased 3'-processing and inefficient nuclear import of reverse transcribed genomes. Solution of the crystal structures of wt and mutated CTDs shows that the motif generates a positive surface potential that is important for integration. The number of charges in the motif appears more crucial than their position within the motif. Indeed, the positions of the K could be permutated or additional K could be inserted in the motif, generally without affecting integration per se. Despite this potential genetic flexibility, the NKNK arrangement is strictly conserved in natural sequences, indicative of an effective purifying selection exerted at steps other than integration. Accordingly, reverse transcription was reduced even in the mutants that retained wt integration levels, indicating that specifically the wt sequence is optimal for carrying out the multiple functions integrase exerts. We propose that the existence of several amino acids arrangements within the motif, with comparable efficiencies of integration per se, might have constituted an asset for the acquisition of additional functions during viral evolution.

中文翻译：

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遗传灵活但保守：HIV-1 M组C-ter结构域的新必需基序整合

使用基于两个系统发育距离较远的分离株（一个来自HIV-1主群M，另一个来自O-1次要O群）的比较的协同进化网络干扰，我们在整合酶的C末端域（CTD）中确定，由四个不连续氨基酸组成的新功能性基序（N ₂₂₂ K ₂₄₀ N ₂₅₄ K ₂₇₃）。通过降低3'加工和逆转录基因组的核输入效率低下，使赖氨酸突变可消除整合。wt和突变的CTD的晶体结构的解决方案表明，该基序产生了一个正向的表面电势，这对于整合非常重要。主题中的电荷数量似乎比它们在主题中的位置更为关键。实际上，通常可以在不影响整合本身的情况下，将K的位置进行排列或在主题中插入其他K。尽管具有这种潜在的遗传灵活性，但NKNK排列严格保留在自然序列中，这表明在整合以外的步骤中可以有效地纯化选择。因此，即使在保留wt整合水平的突变体中，逆转录也减少，这表明wt序列特别适合于发挥整合酶的多种功能。我们提出，基序内几种氨基酸排列的存在，本身具有相当的整合效率，可能已构成在病毒进化过程中获得其他功能的资产。