摘要
Crick(1955)预见到细胞内存在一种小分子RNA称为"衔接子",并假定它是一种沟通DNA与蛋白质序列之间的中介体。Zamecnik(1955)发现sRNA(tRNA),Hoagland(1954)发现氨基酸激活酶(氨基酰-tRNA合成酶)。镁离子稳定tRNA的二级结构(1963),由此,可以得到大的寡核苷酸片断,甚至tRNA的半分子。这项技术大大推动了tRNA及其他RNA序列分析工作的迅速进展。Holley(1965)首次测定出酵母tRNAAla全部核苷酸序列,并设计出一种"三叶草"二级结构。Crick(1966)较早地提出"摆动假说",即反密码子5’端的碱基并不与密码子3’端碱基严格配对,允许有一定的摆动。Rich(1974)等用X射线晶体衍射法,阐明了酵母tRNAPhe的高级结构(呈L型)。2000年,英国剑桥科学家,使用在冰箱保存了15年的酵母tRNAPhe晶体,重新测定它的L型结构是正确的,并严格确定其中10个镁离子和一个精胺分子的精确部位。
Crick （1955） predicted there were ＂adaptors＂ as small RNA molecules in cell and it was postulated to an intermediary between the sequences of DNA and protein.Zamecnik （1955） discovered the sRNA （tRNA） and Hoagland （1954） discovered the amino-acid activating enzyme （aminoacyl-tRNA synthetase） in Zamecnik＇s laboratory.Magnesium ions stabilize the secondary structure of tRNA （1963） and this,in turn,can produce larger fragments or,even two halves of tRNA.This technique greatly promoted the rapid progress of tRNA research.Holley （1965） first determined the complete nucleotide sequence of the yeast alanine tRNA and designated a first ＂cloverleaf＂ of the secondary structure of tRNA.Crick （1966） early devised the wobble concept to explain these problems.It states that the base at the 5＇ end of the anticodon is not as spatially confined as the other two,allowing it to form the hydrogen bonds with any of several bases located at the 3＇ end of a codon.It was proposed that a specific anticodon of tRNA would exist for each codon in the cell.Evidence began to show that highly purified species of known sequence （i.e.,yeast alanine tRNA） could recognize several different codons.Cases were also discovered in which adenine is enzymatically to change into inosine at 5＇ end of anticodon.Rich et al.（1974） elucidated the three-dimensional structure of yeast phenylalanine tRNA by means of X-ray diffraction studies of tRNAPhe crystal.It was found all the double-helical stems predicted by the cloverleaf model for phenylalanine tRNA do in fact exist.After fifteen years （2000）,the crystal of yeast phenylalanine tRNA used for the crystallographic analysis had been stored at 4oC for about 15 years.A total of ten magnesium ions had been assigned exactly.There is also clear density for a spermine molecule binding in the major groove of the TΨC arm.
出处
《生命的化学》
CAS
CSCD
北大核心
2010年第5期656-666,共11页
Chemistry of Life
