Karpel R L, Miller N S, Fresco J R
Biochemistry. 1982 Apr 27;21(9):2102-8. doi: 10.1021/bi00538a019.
The ability of a nucleic acid helix-destabilizing protein from calf thymus, UP1, to facilitate renaturation of yeast tRNALeu3 and Escherichia coli 5S RNA is shown to be a consequence of the protein's ability to bind stoichiometrically to single-stranded polynucleotide regions. A comparison of the inhibitory effect of different homopolymers on UP1-induced renaturation of tRNALeu3 does not indicate significant base specificity in UP1 binding, and a 3'-5' ribose phosphate polymer devoid of heterocyclic bases inhibits as well as the homopolynucleotides. These inhibition studies also show that UP1 requires polynucleotide segments of at least three phosphate residues to bind. Mg2+ (which is required for the stabilization of native tRNALeu3) dissociates complexes of UP1 with inactive tRNA, and since the RNAs in those complexes lack a substantial amount of secondary structure, it can upon dissociation readily refold into the native structure. A semiquantitative treatment of UP1-RNA interaction is developed that suggests that only a small number (approximately six) of protein molecules are bound to tRNALeu3 in the complex while analysis of the inhibition studies suggests that these UP1 molecules are not bound in a highly cooperative manner.
从小牛胸腺中提取的核酸螺旋去稳定蛋白UP1促进酵母tRNALeu3和大肠杆菌5S RNA复性的能力，被证明是该蛋白以化学计量方式结合单链多核苷酸区域的能力的结果。不同均聚物对UP1诱导的tRNALeu3复性的抑制作用比较，并未表明UP1结合存在显著的碱基特异性，且一种不含杂环碱基的3'-5'核糖磷酸聚合物与均聚核苷酸一样具有抑制作用。这些抑制研究还表明，UP1需要至少三个磷酸残基的多核苷酸片段才能结合。Mg2+（天然tRNALeu3的稳定所必需）会使UP1与无活性tRNA的复合物解离，并且由于那些复合物中的RNA缺乏大量二级结构，解离后它可以很容易地重新折叠成天然结构。我们开发了一种对UP1-RNA相互作用进行半定量处理的方法，该方法表明在复合物中只有少数（约六个）蛋白质分子与tRNALeu3结合，而对抑制研究的分析表明，这些UP1分子并非以高度协同的方式结合。
