Department of Bioinformatics, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan.
Protein Sci. 2011 Nov;20(11):1867-75. doi: 10.1002/pro.720. Epub 2011 Sep 22.
β-lactoglobulin (LG) contains nine β-strands (strands A-I) and one α-helix. Strands A-H form a β-barrel. At neutral pH, equine LG (ELG) is monomeric, whereas bovine LG (BLG) is dimeric, and the I-strands of its two subunits form an intermolecular β-sheet. We previously constructed a chimeric ELG in which the sequence of the I-strand was replaced with that of BLG. This chimera did not dimerize. For this study, we constructed the new chimera we call Gyuba (which means cow and horse in Japanese). The amino acid sequence of Gyuba includes the sequences of the BLG secondary structures and those of the ELG loops. The crystal structure of Gyuba is very similar to that of BLG and indicates that Gyuba dimerizes via the intermolecular β-sheet formed by the two I-strands. Thus, the entire arrangement of the secondary structural elements is important for LG dimer formation.
β-乳球蛋白 (LG) 含有九个 β-链（链 A-I）和一个 α-螺旋。链 A-H 形成一个 β-桶。在中性 pH 值下，马 LG (ELG) 是单体，而牛 LG (BLG) 是二聚体，其两个亚基的 I-链形成分子间 β-片层。我们之前构建了一个嵌合 ELG，其中 I-链的序列被 BLG 的序列取代。这个嵌合体没有二聚化。在这项研究中，我们构建了一个新的嵌合体，我们称之为 Gyuba（在日语中是牛和马的意思）。Gyuba 的氨基酸序列包含 BLG 二级结构的序列和 ELG 环的序列。Gyuba 的晶体结构与 BLG 非常相似，表明 Gyuba 通过两个 I-链形成的分子间 β-片层二聚化。因此，二级结构元件的整个排列对于 LG 二聚体的形成很重要。
