通过筛选随机多肽文库研究ZO-1中PDZ1结构域的配体结合特点

选择ZO-1的PDZ1结构域作为研究对象，以酵母双杂交为筛选系统，筛选随机多肽文库和与其它PDZ结构域的配体进行相互作用，阐明ZO-1 PDZ1的配体结合特性.ZO-1 PDZ1识别配体C末端保守的氨基酸序列通式可以表示为：［S/T］［F/Y/W］［V/I/L/C］-COOH、［S/T］［K/R］V-COOH、V［F/Y/W］［L/C］-COOH、EYV-COOH.研究发现ZO-1 PDZ1的配体同时具有3种传统PDZ结构域配体的特点，不同的是其结合配体-1位对芳香族氨基酸具有强烈的偏好性.并且某些PDZ结构域配体的-1位和-3位对结构域与配体相互作用的特异性和亲和力有重要的作用.随后通过生物信息学的方法在Swiss-Prot数据库找到与此识别规律相符合的天然人类蛋白质.根据蛋白质的功能和细胞定位等性质选择10个配体用酵母双杂交验证相互作用.证实的相互作用配体有4个.本研究希望用这样的研究策略建立一种有效的研究蛋白质相互作用的方法，通过在全蛋白质组规模上对含有结合配体保守氨基酸序列的蛋白质的查询，理论上可以找到现有数据库中所有可能与目的结构域结合的潜在配体蛋白，特别是那些筛选cDNA文库不容易获得的低丰度配体.

Ligand-binding Characterization of PDZ1 Domain in ZO-1 by Screening Random Peptide Library

This study focused on exploring the ligand binding characteristics of the PDZ1 domain in ZO-1 by screening random peptide library and crossing interaction with the other PDZ domain ligands by yeast two hybrid. The C terminal consensus sequences for the PDZ binding are ［S/T］［F/Y/W］［V/I/L/C］-COOH，［S/T］［K/R/H］［V/I/L］-COOH，［V/I/L］［F/Y/W］［V/I/L/C］-COOH，［D/E］［F/Y/W］［V/I/L］-COOH. This indicates that ZO-1PDZ1 binds classical type Ⅰ, Ⅱ, and Ⅲ ligands with a strong preference for aromatic residues at position -1. These results indicate the importance of the position -1 and- 3 of some PDZ domains to the binding specificity and affinity. Moreover, sequences of native human proteins with the same predicted C terminal motifs were identified by searching the protein databank Swiss Prot. Ten native human proteins were chosen by their cellular locations and biological functions for validation by yeast two hybrid and four of them were confirmed positive. The strategy of screening random peptide library combined with bioinformatics established in this work can be an effective approach, which theoretically can identify all the potential ligands in the databases, especially those low abundant ligands rarely obtained by screening a cDNA library.