Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892-0520, USA.
Protein Sci. 2010 Nov;19(11):2055-72. doi: 10.1002/pro.486.
The mature protease from Group N human immunodeficiency virus Type 1 (HIV-1) (PR1(N)) differs in 20 amino acids from the extensively studied Group M protease (PR1(M)) at positions corresponding to minor drug-resistance mutations (DRMs). The first crystal structure (1.09 Å resolution) of PR1(N) with the clinical inhibitor darunavir (DRV) reveals the same overall structure as PR1(M), but with a slightly larger inhibitor-binding cavity. Changes in the 10s loop and the flap hinge propagate to shift one flap away from the inhibitor, whereas L89F and substitutions in the 60s loop perturb inhibitor-binding residues 29-32. However, kinetic parameters of PR1(N) closely resemble those of PR1(M), and calorimetric results are consistent with similar binding affinities for DRV and two other clinical PIs, suggesting that minor DRMs coevolve to compensate for the detrimental effects of drug-specific major DRMs. A miniprecursor (TFR 1-61-PR1(N)) comprising the transframe region (TFR) fused to the N-terminus of PR1(N) undergoes autocatalytic cleavage at the TFR/PR1(N) site concomitant with the appearance of catalytic activity characteristic of the dimeric, mature enzyme. This cleavage is inhibited at an equimolar ratio of precursor to DRV (∼6 μM), which partially stabilizes the precursor dimer from a monomer. However, cleavage at L34/W35 within the TFR, which precedes the TFR 1-61/PR1(N) cleavage at pH ≤ 5, is only partially inhibited. Favorable properties of PR1(N) relative to PR1(M) include its suitability for column fractionation by size under native conditions and >10-fold higher dimer dissociation constant (150 nM). Exploiting these properties may facilitate testing of potential dimerization inhibitors that perturb early precursor processing steps.
N 组人类免疫缺陷病毒 1 型(HIV-1)(PR1(N))的成熟蛋白酶与广泛研究的 M 组蛋白酶(PR1(M))在对应于次要耐药突变(DRMs)的位置上有 20 个氨基酸不同。具有临床抑制剂达芦那韦(DRV)的 PR1(N)的第一个晶体结构(1.09Å分辨率)显示出与 PR1(M)相同的整体结构,但抑制剂结合腔略大。10s 环和瓣铰链的变化导致一个瓣向抑制剂移动,而 L89F 和 60s 环中的取代会扰乱抑制剂结合残基 29-32。然而,PR1(N)的动力学参数与 PR1(M)非常相似,量热学结果与 DRV 和另外两种临床 PI 的相似结合亲和力一致,表明次要 DRMs 共同进化以补偿特定药物的主要 DRMs 的有害影响。包含跨框架区(TFR)与 PR1(N)的 N 端融合的小前体(TFR 1-61-PR1(N))在 TFR/PR1(N)位点上进行自动催化切割,同时出现特征为二聚体、成熟酶的催化活性。这种切割在与 DRV 等摩尔比(约 6μM)的前体抑制剂下被抑制,这部分稳定了来自单体的前体二聚体。然而,在 pH≤5 时,在 TFR 1-61/PR1(N)切割之前的 TFR 内的 L34/W35 处的切割仅被部分抑制。PR1(N)相对于 PR1(M)的有利特性包括其在天然条件下通过大小进行柱分级的适宜性和二聚体解离常数高 10 倍以上(150nM)。利用这些特性可能有助于测试干扰早期前体加工步骤的潜在二聚体抑制剂。