Guan Siyu, Tan Suet-Mien, Li Yan, Torres Jaume, Alex Law S K
School of Biological Sciences, Nanyang Technological University, Singapore.
Biochem Biophys Rep. 2016 Jun 20;7:214-217. doi: 10.1016/j.bbrep.2016.06.013. eCollection 2016 Sep.
We showed that the αLβ2 integrin with the non-functional mutation G150D cannot be induced with Mg/EGTA to express the mAb KIM127 epitope, which reports the leg-extended conformation. We extended the study to the αIIbβ3, an integrin without an αI domain. The equivalent mutation, i.e. G161D, also resulted in an expressible, but non-adhesive αIIbβ3 integrin. An NMR study of synthetic peptides spanning the α1-α1' helix of the β3 I domain shows that both wild-type and mutant peptides are α-helical. However, whereas in the wild-type peptide this helix is continuous, the mutant presents a discontinuity, or kink, precisely at the site of mutation G161D. Our results suggest that the mutation may lock integrin heterodimers in a bent conformation that prevents integrin activation via conformational extension.
我们发现，带有无功能突变G150D的αLβ2整合素不能用Mg/EGTA诱导表达报告腿部伸展构象的单克隆抗体KIM127表位。我们将研究扩展到αIIbβ3，一种没有αI结构域的整合素。等效突变，即G161D，也导致了一种可表达但无粘附性的αIIbβ3整合素。对跨越β3 I结构域α1-α1'螺旋的合成肽进行的核磁共振研究表明，野生型和突变型肽均为α螺旋结构。然而，野生型肽中的这种螺旋是连续的，而突变型肽恰好在突变位点G161D处出现了不连续或扭结。我们的结果表明，该突变可能将整合素异二聚体锁定在弯曲构象中，从而阻止通过构象延伸激活整合素。
