酵母菌 Bcp1 蛋白的結構研究

Abstract

核醣體的功能為蛋白質轉譯。核糖體生合成需要耗費許多能量，而且糖體蛋白需要與 rRNA 進行組裝，會有較鬆散的延伸區域，所以細胞會以 dedicated chaperone 伴護核糖體蛋白，在實驗室前人的研究中發現酵母菌 Bcp1 蛋白是核糖體大次單元蛋白 Rpl23 的 dedicated chaperone，Bcp1 會在 Rpl23 入核後，將其從核轉運蛋白 (Karyopherin, Kap) 上釋放，但是其伴護及釋放機制仍不清楚，所以本篇研究從結構的部分下手，先解出 Bcp1 的結構，並且試圖分析 Bcp1- Rpl23 複合體的結構，接者以突變的方式，確認 Rpl23 以其環狀區域 41-52 號胺基酸進行交互作用，而且兩者是以疏水性交互作用力結合，透過兩者的交互作用 Bcp1 才能將 Rpl23 從 Karyopherin 上釋放。在 Rpl23 Lys106/Lys110 修飾的雙甲基化，有助於與 Tif6 結合。另一方面確定 Mss4 會透過 Bcp1 參與核糖體大次單元生合成。

The function of ribosome is protein translation. Ribosome biogenesis cost a lot of energy. While ribosomal proteins assemble with rRNAs, they evolve to have loose extenions. In consequence, cells use dedicated chaperones to protect ribosomal proteins. According to our previous study, yeast Bcp1 protein is the dedicated chaperone of large ribosomal subunit protein, Rpl23. Bcp1 could release Rpl23 from karyopherin (Kap), however, the mechanism behind the protection and release is still unknown. Therefore, this study attempts to determin the crystal structure of Bcp1 and analyze how Bcp1 intercats with Rpl23. From mutagenesis study, Rpl23 was found to use the interal loop, amino acid 41-52, to intercat with Bcp1. And this interaction was stabilized by hydrophobic interaction. Bcp1 could release Rpl23 from Kap through the direct interaction with Rpl23 but not with Kap. The dimethylations on Lys106/Ly110 of Rpl23 were found to enhance the binding with Tif6. In additional, Mss4 may involve in biogenesis of large ribosomal subunit through Bcp1.