蓝氏贾第虫组蛋白的初步研究

PRELIMINARY STUDY ON THE HISTONES OF Ciardia lamblia

本文初步比较分析了贾第虫组蛋白的存在及其基本组成。通过甲醇固定，两次０．３ｍｏｌ／ＬＨＣｌ抽提及丙酮沉淀，提取贾第虫酸溶性蛋白，利用亲和层析制取总ＤＮＡ结合蛋白，经酸性尿素系统及ＳＤＳ系统电泳分析表明，贾第虫已存在５种组蛋白，其在两种不同性质电泳系统中的电泳行为与相应的小牛胸腺组蛋白有近似的对应关系。说明贾第虫的组蛋白已发生了分化，并已初步形成了性质不同的几个组份，从而在一定程度上支持核小体组蛋白在真核生物的原核祖先阶段就已产生了分化的假说。

About how the prokaryotic ancestor molecular of core histones evolved into four kinds of core histones of eukaryote has two possibilities: one is the ancestral molecular had already differentiated into four kinds at stage of prokaryote, the other is this differentiation occurred after the cell evolving into the eukaryotic cell. HMf and HMt, two kinds of histone-related proteins, isolated respectively from Methanothermus fervidus and Methanobacterium thermoautotrophicum △H, Archaebacteria which are most closely related to eukaryote, by reeve's laboratory have already differentiated into HMf1, HMf2 and HMt1, HMt2. UP to now, the core histones found from lower qukaryotic cell, such as Leishmania and Tetrahymena, have all differentiated into four kinds. In this paper, the total histones were prepared from Giardia lamblia, the most primitive eukaryotic cell,,by engaging in methanol prefixation, two times of 0.3 mol / L HCl extraction, acetone precipitation and DNA affinity chromatography. The results of electrophoresis, SDS gel (Fig.1) and acid urea gel (Fig.2), of the Giardia histones showed that seven major protein bands could be resolved, and five of these bands migrated to position similar those of five kinds of calf thymus pistones. It seems,therefore, that the Giardia histones have already differentiated and consisted of at least five kinds of histones, and, on certain extent, this supported the hypothesis that the histone had already differentiated into four different kinds at the stage of prokaryotic ancestor of eukaryote.