反相高效液相色谱法测定五肽胃泌素及其酶促降解产物

在反相ODS柱上,用NH_4Ac-HAc缓冲溶液和甲醇作流动相进行梯度洗脱,清晰地分离了五肽胃泌素及其酶促降解产物。HPLC法分离简便,定量准确,可有效地用于研究活性多肽的酶促降解机制。通过HPLC法探讨五肽胃泌素的降解过程尚属首次。     

一个不寻常的人λ-型Bence Jones蛋白(Lee)可变区的氨基酸序列

用限制性胰蛋白酶水解,制备了人λ-型Bence Jones蛋白(Lee)的可变区,用还原并氨乙基化的蛋白质制备了溴化氰裂解片段和胰蛋白酶水解肽,测定各肽段的氨基酸序列并根据Lee蛋白和其它λ-链的同源性定出了Lee轻链可变区的氨基酸全序列。Lee轻链的N末端有二个额外氨基酸残基的延伸。Lee蛋白的个体型(idiotypic)抗体能和另外两个λ-型Bence Jones蛋白MCg λ_Ⅳ和Cap λ_Ⅲ反应。用Chou和Fasman的方法预测Lee轻链可变区二级结构的结果表明:Lee轻链可变区表面上有两个部分和Mcg,Cap的相应部分的结构相同,这是这三个蛋白质在免疫学性质上具有个体型相似性的可能解释。     

AMINO ACID SEQUENCE OF THE VARIABLE REGION OF AN UNUSUAL λ-TYPE HUMAN BENCE JONES PROTEIN (LEE)

The variable portion of a human λ-type Bence Jones protein (Lee) has been prepared by limited tryptic digestion. Its amino acid sequence is determined from analysis of tryptic peptides, CNBr cleavage fragments prepared from the reduced-aminocthylated protein. Peptides are aligned by homology to other λ-type proteins. The Lee L-chain has an unusual extension of two amino acid residues (Val-Thr) at the N-terminus. An idiotypic antibody of Lee can react with two other λ-type Bence Jones proteins, Meg (V_λⅣ) and Cap (V_2 Ⅲ). Application of the principle of Chou and Fasman to the sequence data indicates that two portions on the surface of the Ⅴ-region have identical secondary structures similar to the portions of the Meg and Cap λ-chains. This appears to relate to the idiotypic similarities of the three proteins.