The Biodiversity of the Basic Chromatin Proteins of Archaebacteria in China

Abstract

Using a novel acid extraction procedure.the acid—soluble proteins from a thermo—and acido-philic archaebacterium Suifosphaerelus thermoacidophilum were isolated,and analysised by SDS-PAGE and AUT—PAGE with the calf thymus histones.which were isolated by the same procedure,as a contro1. The neutral Azocarmin G staining technique,which specificaly stains basic chromatin protein。was used. The results suggested that the archaebacterium owns three major basic chromatin proteins.the molecular weight of al the basic proteins was smaUer than calf thymus histone H4 (MW 1 1 282). Different artchaebacterium possesses very different basic chromatin (histone—like)proteins.The biodiversity of these proteins was very rich.The significance of their biodiversity to the origin and evolution of histone was discussed. Ke wards archaebacteria.basic chromatin protein.biodiversity histone evlution Archaebacteria are a group of prokaryotes, which are very different from another group of prokaryotes—eubacteria such as E.coli.Since the discovery of archaebac4eria in the late 1 970s,the growing evidences,especialy of molecular biology, strongly suggests that they have much closer evolutionary relationship with eukaryotic cel than eubacteria do. The discovery of archaebacteria sheds new light on the mystery of the origin and evolutin of eukaryotic cel1. Almost every typic eukaryotic cell owns the basic chromatin protein—————histone.It is also clear that histone (H1,H2A,H2B.H3,H4)is very conserved among different eukaryotes.and the four core histones have a high homology to each other,they must come from a common ancestral protein (Reeck et a1.1 978).But what is the ancestral protein and where to find it?Although a lot of work about this have been done on lower eukaryotes such as dinoflagellates and on prokaryotes eubacteria , no significant clue was found. W hile on archaebacteria this is not the case at al1.Up to now , no common basic chromatin protein was discovered in them.they are different in different species . It is the difference (or biodiversity)that provides the possibility for us to find some evolutionary clue of histone in archaebacteria.In fact.some interesting results have been obtained,the HMf , HM t,HM v proteins, for instance, are three basic chromatin proteins discovered in three methanogenic archaebacteria,they have a very high homology to the four core histones (Sandman et a1 . 1 990: Tabassum et a1.1992:Agha—Amiri and Klein 1993).In the present work,we have investigated the ·66· 维普资讯 http://www.cqvip.com