丝瓜蛋白及与AMP相互作用的晶体结构研究

beta-luffin is a kind of type I ribosome-inactivating protein extracting from sponge gourd seeds(Luffa cylindrica),which possesses RNA N-glycosidase activity. It can inhibit the protein synthesis in eukaryotic cells by inactivating the ribosomes.The crystals suitable for X-ray diffraction were obtained by hanging-drop vapor diffusion method in the room temperature.The crystals belong to the space group C2, with unit-cell parameters a=89.90A，b=59.82A,c=55.16A,β=120.81°, and have one molecule in the crystallographic asymmetric unit. The X-ray diffraction data were processed by the DENZO & SCALEPACK program. Which have the highest resolution of 2.0A and the completeness of 99.6%.The crystal structure of beta-luffin at 2.0A resolution was solved by molecular replacement method using polyalanined trichosanthin as the search model.The structure was refined with CNS1.1,giving Rwork=0.162, Rfree=0.204.The rmsd of bond lengths and bond angles are 0.008A and 1.3° respectively.The overall structure is similar to those of other type I RIPs. Three N-acetylglucosamines(Nag) molecules linked to residues Asn2, Asn78 and Asn85 of protein are included in the final model.

丝瓜蛋白-α是单链核糖体失活蛋白(I型RIP). 它是目前发现的单链RIPs 中活性最高的. 它的无细胞系统抑活能力比蓖麻A链高5.5倍. 且含六个可能的糖基结合位点. 测定它的结构及其与AMP相互作用形成的复合物结构并与已知结构的同源蛋白进行比较对探索核糖体失活蛋椎慕峁褂牍δ芄叵涤兄卮笠庖?