Shiroishi Mitsunori, Maenaka Katsumi
Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Protein Pept Lett. 2009;16(4):447-9. doi: 10.2174/092986609787848108.
Human leukocyte antigen-G (HLA-G) is a nonclassical MHC class I (MHCI) molecule that is expressed mainly on placenta trophoblast cells. Leukocyte Ig-like receptor B2 (LILRB2) is a human inhibitory immune receptor that recognizes HLA-G with a higher affinity than any other MHCI although this interaction is only in the microM range. The interaction between HLA-G and LILRB2 seems to play a dominant role in the escape of the fetus from the maternal immune response. Here we report the crystallization and x-ray analysis of the LILRB2/HLA-G complex. The extracellular domains of HLA-G and LILRB2 were expressed in Escherichia coli, refolded and purified. The initial crystallization trials using novel PEG-based screening sets provided crystals of the LILRB2/HLA-G complex with 40-50% PEG400 as the precipitant. These crystals belong to space group P3(1)21 (a=b=81.4 A, c=186.7 A, gamma=120 degrees ). Dehydration of the crystals by soaking them in a solution containing a higher concentration of PEG400 dramatically improved the resolution and also the mosaicity.
人类白细胞抗原G（HLA - G）是一种非经典的MHC I类（MHCI）分子，主要表达于胎盘滋养层细胞。白细胞免疫球蛋白样受体B2（LILRB2）是一种人类抑制性免疫受体，它识别HLA - G的亲和力高于任何其他MHCI，尽管这种相互作用仅在微摩尔范围内。HLA - G与LILRB2之间的相互作用似乎在胎儿逃避母体免疫反应中起主导作用。在此我们报告LILRB2/HLA - G复合物的结晶及X射线分析。HLA - G和LILRB2的细胞外结构域在大肠杆菌中表达、重折叠并纯化。使用新型基于聚乙二醇（PEG）的筛选试剂盒进行的初步结晶试验，得到了以40 - 50% PEG400作为沉淀剂的LILRB2/HLA - G复合物晶体。这些晶体属于空间群P3(1)21（a = b = 81.4 Å，c = 186.7 Å，γ = 120°）。通过将晶体浸泡在含有更高浓度PEG400的溶液中进行脱水，显著提高了解析度以及镶嵌性。
