CRYSTAL-STRUCTURES OF CYCLOPHILIN-A COMPLEXED WITH CYCLOSPORINE-A AND N-METHYL-4-[(E)-2-BUTENYL]-4,4-DIMETHYLTHREONINE CYCLOSPORINE-A
CRYSTAL-STRUCTURES OF CYCLOPHILIN-A COMPLEXED WITH CYCLOSPORINE-A AND N-METHYL-4-[(E)-2-BUTENYL]-4,4-DIMETHYLTHREONINE CYCLOSPORINE-A
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DOI：
10.1016/s0969-2126(00)00006-x
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发表时间：
1994-01-15
期刊：
影响因子：
5.7
通讯作者：
WALSH, CT
中科院分区：
文献类型：
--
作者：
KE, HM;MAYROSE, D;WALSH, CT
背景：亲环素是一种普遍存在的细胞内蛋白，与免疫抑制药物环孢素A(CsA)结合。CYP-CsA与钙调神经磷酸酶形成三元复合体，从而抑制T细胞的激活。结果：我们确定了人亲环素A(CyPA)与环孢素A(CsA)的络合物结构，分辨率为2.1埃。我们还报道了环孢素A与环孢素A的类似物N-methyl-4-[(E)-2-butenyl]-4，4-dimethylthreonine环孢素A(MeBm(2)tl-环孢素A)的结构，它与环孢素A结合较差，但具有增强免疫抑制活性。将这些结构与先前确定的未连接的CyPA和CyPA与异构酶活性的候选底物AlaPro络合的结构进行比较，发现CsA和CyPA在形成络合物时都发生了微妙的构象变化。结论：MeBm(2)tl-CsA以与CsA基本相似的方式与CyPA结合。其结合亲和力降低100倍可能是由于MeBmt1与CyPA的活性部位残基Ala103紧密接触，导致蛋白质和药物的构象发生微小变化。一个变化是CsA中MeLeu6相对于MeBm(2)tl-CsA的轻微移动，这可能至少部分是CyPA-MeBm(2)tl-CsA复合体对钙调神经磷酸酶有更高的亲和力的原因。我们对CyPA-CSA和CyPA-AlaPro的比较表明，CsA可能不是天然底物的类似物，证实了CyPA的催化活性无论在结构上还是在功能上都与其在免疫抑制中的作用无关。
Background: Cyclophilin (CyP) is a ubiquitous intracellular protein that binds the immunosuppressive drug cyclosporin A. (CsA). CyP-CsA forms a ternary complex with calcineurin and thereby inhibits T-cell activation. CyP also has enzymatic activity, catalyzing the cis-trans isomerization of peptidyl-prolyl amide bonds.Results: We have determined the structure of human cyclophilin A (CyPA) complexed with CsA to 2.1 Angstrom resolution. We also report here the structure of CyPA complexed with an analog of CsA, N-methyl-4-[(E)-2-butenyl]-4,4-dimethylthreonine CsA (MeBm(2)tl-CsA), which binds less well to CyPA, but has increased immunosuppressive activity. Comparison of these structures with previously determined structures of unligated CyPA and CyPA complexed with a candidate substrate for the isomerase activity, the dipeptide AlaPro, reveals that subtle conformational changes occur in both CsA and CyPA on complex formation.Conclusions: MeBm(2)tl-CsA binds to CyPA in an essentially similar manner to CsA. The 100-fold weaker affinity of its binding may be attributable to the close contact between MeBmtl and the active site residue Ala103 of CyPA, which causes small conformational changes in both protein and drug. One change, the slight movement of MeLeu6 in CsA relative to MeBm(2)tl-CsA, may be at least partially responsible for the higher affinity of the CyPA-MeBm(2)tl-CsA complex for calcineurin. Our comparison between CyPA-CsA and CyPA-AlaPro suggests that CsA is probably not an analog of the natural substrate, confirming that the catalytic activity of CyPA is not related to its role in immunosuppression either structurally or functionally.