Kuil Joeri, van Wandelen Loek T M, de Mol Nico J, Liskamp Rob M J
Medicinal Chemistry and Chemical Biology, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Utrecht, The Netherlands.
J Pept Sci. 2009 Oct;15(10):685-91. doi: 10.1002/psc.1173.
Spleen tyrosine kinase (Syk) plays an essential role in IgE receptor signaling (FcepsilonRI), which leads to mast cell degranulation. Divalent binding of the tandem SH2 domain (tSH2) of Syk to the intracellular ITAM motif of FcepsilonRI activates the kinase domain of Syk, and thereby initiates cell degranulation. The inter SH2 domain distance in Syk tSH2 might be important for Syk kinase activation. In this study, photoswitchable ITAM peptidomimetics containing an azobenzene moiety were synthesized. Irradiation of these constructs changes the distance between the two SH2 binding epitopes and therefore, they may be used as photoswitches. The affinity of the cis- and trans-isomer for tSH2 was assayed with SPR. The ITAM peptidomimetic with the smallest linker displayed the largest difference in affinity between the two isomers (at least 100-fold), and the affinity of the cis-isomer was comparable to monovalent binding. The ITAM mimics with larger photoswitchable linkers displayed modest differences. These results indicate that Syk tSH2 is able to adapt the inter SH2 domain distance to ligands larger than native ITAM, but not to smaller ones.
脾酪氨酸激酶（Syk）在IgE受体信号传导（FcepsilonRI）中起关键作用，该信号传导会导致肥大细胞脱颗粒。Syk的串联SH2结构域（tSH2）与FcepsilonRI的细胞内免疫受体酪氨酸激活基序（ITAM）的二价结合激活了Syk的激酶结构域，从而引发细胞脱颗粒。Syk tSH2中SH2结构域之间的距离可能对Syk激酶激活很重要。在本研究中，合成了含有偶氮苯部分的光开关ITAM拟肽。这些构建体的照射改变了两个SH2结合表位之间的距离，因此，它们可用作光开关。用表面等离子体共振（SPR）测定顺式和反式异构体对tSH2的亲和力。具有最短连接子的ITAM拟肽在两种异构体之间显示出最大的亲和力差异（至少100倍），并且顺式异构体的亲和力与单价结合相当。具有较大光开关连接子的ITAM模拟物显示出适度差异。这些结果表明，Syk tSH2能够使SH2结构域之间的距离适应大于天然ITAM的配体，但不能适应较小的配体。
