Aruga J, Okano H, Mikoshiba K
Institute for Protein Research, Osaka University, Japan.
J Neurochem. 1991 Apr;56(4):1222-6. doi: 10.1111/j.1471-4159.1991.tb11414.x.
Myelin basic protein (MBP) is a major constituent in the myelin of the CNS. In mice, five forms of MBPs (14 kDa, two types of 17 kDa, 18.5 kDa, and 21.5 kDa) encoded by separate mRNAs have been identified based on cDNA cloning studies. These mRNAs are considered to be produced by alternative splicing from a single gene composed of seven exons. Here we report the existence of two novel MBP mRNAs encoding 19.7-kDa and 21-kDa MBPs identified by cDNA cloning using the polymerase chain reaction. Both of these MBPs contain a sequence of a previously unidentified exon of 66 nucleotides, which was mapped to be just 5' of exon 5 in the MBP gene. MBP mRNAs containing this novel exon (exon 5a) belong to a minor population in the whole brain and PNS and are somewhat enriched in the spinal cord. Exon 5a encodes a very hydrophobic segment rich in valine residues, which presumably forms a beta-pleated sheet.
髓鞘碱性蛋白（MBP）是中枢神经系统髓鞘的主要成分。在小鼠中，基于cDNA克隆研究已鉴定出由单独的mRNA编码的五种形式的MBP（14 kDa、两种类型的17 kDa、18.5 kDa和21.5 kDa）。这些mRNA被认为是由一个由七个外显子组成的单一基因通过可变剪接产生的。在此，我们报告通过使用聚合酶链反应进行cDNA克隆鉴定出两种编码19.7 kDa和21 kDa MBP的新型MBP mRNA。这两种MBP均包含一个66个核苷酸的先前未鉴定外显子序列，该序列被定位在MBP基因中外显子5的5'端。包含这个新外显子（外显子5a）的MBP mRNA在全脑和外周神经系统中属于少数群体，并且在脊髓中略有富集。外显子5a编码一个富含缬氨酸残基的非常疏水的片段，推测该片段形成β折叠片层。
