Yamanashi Y, Miyasaka M, Takeuchi M, Ilic D, Mizuguchi J, Yamamoto T
Institute of Medical Science, University of Tokyo, Japan.
Cell Regul. 1991 Dec;2(12):979-87. doi: 10.1091/mbc.2.12.979.
We previously cloned a lyn cDNA-encoding 56-kd Src-like protein-tyrosine kinase, p56lyn. Anti-Lyn antibodies raised against a sequence of 95 amino acids (Arg-25 to Ala-119 of p56lyn) recognized two species of the protein, p56lyn and p53lyn. V8 proteinase analysis showed that p53lyn differs only slightly from p56lyn. Analysis of mRNA from B lymphocytes by the polymerase chain reaction indicated the presence of two forms of alternatively spliced lyn mRNA. Nucleotide sequencing of the corresponding cDNAs revealed that these two forms of lyn mRNA differ in the presence and absence of a 63 nucleotides sequence near the 5'-terminus of the coding region; 21 amino acid residues (Pro-23 to Arg-43 or Val-24 to Pro-44) of p56lyn were tentatively concluded to be missing in p53lyn. On cross-linking of the membrane-bound IgM (mIgM) on the surface of B lymphocytes, the kinetics of down-regulations of the two Lyn proteins demonstrated to be associated with the mIgM antigen receptor were found to be different. This observation suggests that the amino terminal proximal sequence of the Lyn protein is important for determining its mode of interaction with mIgM.
我们之前克隆了一个编码56-kd Src样蛋白酪氨酸激酶p56lyn的lyn cDNA。针对95个氨基酸序列（p56lyn的第25位精氨酸至第119位丙氨酸）产生的抗Lyn抗体识别出该蛋白的两个种类，即p56lyn和p53lyn。V8蛋白酶分析表明p53lyn与p56lyn仅略有不同。通过聚合酶链反应对B淋巴细胞的mRNA进行分析，结果表明存在两种形式的选择性剪接lyn mRNA。对相应cDNA进行核苷酸测序发现，这两种形式的lyn mRNA在编码区5'-末端附近63个核苷酸序列的有无上存在差异；初步推断p53lyn中缺少p56lyn的21个氨基酸残基（第23位脯氨酸至第43位精氨酸或第24位缬氨酸至第44位脯氨酸）。在B淋巴细胞表面的膜结合IgM（mIgM）交联时，发现与mIgM抗原受体相关的两种Lyn蛋白下调的动力学有所不同。这一观察结果表明，Lyn蛋白的氨基末端近端序列对于确定其与mIgM的相互作用方式很重要。
