Scherberg N, Refetoff S
Biochim Biophys Acta. 1977 Mar 18;475(2):337-51. doi: 10.1016/0005-2787(77)90024-7.
Bound iodine is released from radioiodinated nucleotides in polymers exposed to sodium bisulfite. The rate of bisulfite-catalyzed deiodination of pyrimidines can be controlled both by change of temperature of pH and is also dependent on the molecular association of the nucleotide. The rate of release of iodine from iodocytidine in polycytidylate is greater than the rate of elimination from RNA. Experiments testing the influence of base-pairing of the iodopyrimidines in synthetic polynucleotides showed that pairing of the substituted nucleotide protected the iodine bond. The rates of bisulfite-catalyzed deiodination of several radioiodinated RNAs were measured. The action of bisulfite on all single stranded RNAs tested was multiphasic consisting of a rapid early deiodination reaction supplanted by a slower phase which was followed by reacceleration of release. The release of iodine from double stranded RNA and DNA-RNA duplexes was retarded in comparison with the release from ribosomal and messenger RNA fractions. The deiodination profiles of single and double stranded RNA suggested that the intermediate stage iodine release is governed by melting of paired zones of low stability. Late release may result from destablization of the molecule through the addition of bisulfite to the pyrimidine ring or deamination. The effect of several substances expected to complex with polynucleotides was tested. Acridine orange and ethidium bromide increased loss of iodine from ribosomal RNA but slightly decreased elimination from double stranded viral RNA. A basic protein fraction isolated from ribosomal particles accelerated the deiodination of ribosomal RNA. While the destabilization caused by this protein fraction was greater than that caused by an equal amount of albumin, as tested the effect was non-specific. The results show that a change in sensitivity to chemical deiodination may folow the interaction of small amounts of protein with polynucleotides.
结合碘从暴露于亚硫酸氢钠的聚合物中的放射性碘化核苷酸中释放出来。亚硫酸氢盐催化的嘧啶脱碘速率可通过改变pH温度来控制，并且还取决于核苷酸的分子缔合。聚胞苷酸中碘胞苷的碘释放速率大于RNA中的消除速率。测试合成多核苷酸中碘嘧啶碱基配对影响的实验表明，取代核苷酸的配对保护了碘键。测量了几种放射性碘化RNA的亚硫酸氢盐催化脱碘速率。亚硫酸氢盐对所有测试的单链RNA的作用是多相的，包括快速的早期脱碘反应，随后是较慢的阶段，接着是释放的重新加速。与核糖体和信使RNA组分的释放相比，双链RNA和DNA-RNA双链体中碘的释放受到抑制。单链和双链RNA的脱碘曲线表明，中间阶段的碘释放受低稳定性配对区解链的控制。后期释放可能是由于嘧啶环添加亚硫酸氢盐或脱氨导致分子不稳定所致。测试了几种预期与多核苷酸络合的物质的作用。吖啶橙和溴化乙锭增加了核糖体RNA中碘的损失，但略微降低了双链病毒RNA中的消除。从核糖体颗粒中分离出的一种碱性蛋白质组分加速了核糖体RNA的脱碘。虽然该蛋白质组分引起的不稳定大于等量白蛋白引起的不稳定，但测试表明该作用是非特异性的。结果表明，少量蛋白质与多核苷酸相互作用后，对化学脱碘的敏感性可能会发生变化。
