保守的第52位色氨酸突变引起的胰高血糖素样肽1受体N端片段活性丧失

Conserved W^(52) led to reduced binding of glucogan-like peptide 1 receptor

通过易错PCR方法建立了一个鼠肺不同长度的nGLP-1R(从第21个氨基酸开始到第145个氨基酸)的噬菌体随机突变展示肽库,通过噬菌体表面展示技术检测胰高血糖素样肽1受体N端片段(nGLP-1R)在缺失一段或两段基因后是否还具有结合Exendin-4的活性。经ELISA分析发现了一株无结合活性的突变株,命名为EP16。经测序比对,发现EP16缺失了前20个和后10个氨基酸,且第52位色氨酸突变为精氨酸。为确定EP16与Exendin-4无结合活性的原因,重新构建了无前20个和后10个氨基酸的EP16野生型及第52位色氨酸变为精氨酸的全长nGLP-1RW52R与EP16进行对比分析。结果表明,EP16的活性丧失是由保守的第52位色氨酸突变为精氨酸引起的,缺失的前20个和后10个氨基酸没有影响其生物学活性。关键位点单个氨基酸残基的突变可以改变胰高血糖素样肽1受体N端片段整个蛋白质的生物学活性。

Through phage display, we tried to find out whether the N-terminal fragment of glucogan-like peptide 1 receptor （nGLP-1R） still had binding activity to Exendin-4 after missing one or two gene segments. By error-prone PCR, We constructed a randomly mutated phage display peptide library with different length of the N-terminal （21-145 residues） extracellular domain of glucogan-like peptide 1 receptor （GLP-1R） from rat lung. A mutant named EP16 without binding activity was found by ELISA. Through sequence alignment we found that EP16 missed the first 20 and last 10 amino acids and the 52na tryptophan was mutated to arginine. In order to determine why Ep16 did not show its binding ability to Exendin-4, a wild type EP16 without the first 20 and last 10 amino acids and nGLP-1RW52R was constructed in which the 52nd tryptophan was mutated to arginine. The contrastive analysis showed that the substitution of W52R led to a markedly reduced binding ability of EP16. The mutation of the conserved W52 could change the biologic activity of the protein. The lack of the first 20 and last 10 amino acids had no effect on its biologic activity. Therefore, the mutation of a single amino acid residue of the key sequence could change the biologic activity of the nGLP-1R.