STRUCTURAL-ANALYSIS OF SELF-REPLICATING RNA SYNTHESIZED BY Q-BETA REPLICASE
STRUCTURAL-ANALYSIS OF SELF-REPLICATING RNA SYNTHESIZED BY Q-BETA REPLICASE
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DOI：
10.1016/s0022-2836(82)80019-3
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发表时间：
1982-01-01
影响因子：
5.6
通讯作者：
LUCE, R
中科院分区：
文献类型：
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作者：
BIEBRICHER, CK;DIEKMANN, S;LUCE, R
RNA变体MNV-11（86个碱基对）通过Q β的自我复制在盐存在下，复制酶导致逐步选择更耐盐的变异体SV-11（113个碱基对）和MDV-1（220个碱基对）。这些和其他2个不相关的耐盐变体的结构进行了比较。所有变体可以作为双链或单链RNA存在。双链RNA的协同热变性需要约100 ℃或甚至高于100 ℃的高温。C.双链RNA分子具有高的负电二向色性，并且如果假设RNA为A-形式而DNA为B-形式，则它们的极化率和旋转扩散常数显示与双链DNA相同的长度依赖性。单链RNA在高温下也具有尖锐的熔点和相当高的增色性，揭示了单链RNA的强二级结构。更耐盐的变体具有更高的熔点和增色性。单链RNA的解链温度比同一物种的双链RNA低几度，除了单链MDV-1，它的解链温度与双链RNA相同。随着单链RNA二级结构的增加，其退火形成双链的速率降低。单链变体既是复制的直接产物（复制品），也是首选模板。SV-11具有2种单链RNA形式，其中只有一种能够作为Q β的活性模板。复制酶它的非活性单链形式更稳定，显然具有发夹结构。在复制中活跃的单链RNA具有消失的电二向色性，这表明确定的三级结构不允许茎和环在电场中独立取向。
Self-replication of the RNA variant MNV-11 (86 base-pairs) by Q.beta. replicase leads, in the presence of salt, to stepwise selection of the more salt-resistant variants SV-11 (113 base-pairs) and MDV-1 (220 base-pairs). The structures of these and 2 other unrelated salt-resistant variants are compared. All variants can exist as double-stranded or as single-stranded RNA. The cooperative thermal denaturation of double-stranded RNA requires high temperatures, around or even above 100.degree. C. Double-stranded RNA molecules have high negative electric dichroisms and their polarizabilities and rotational diffusion constants show the same length dependences as double-stranded DNA if RNA is assumed to be in the A-form and DNA in the B-form. The single-stranded RNA also have sharp melting points at high temperatures and rather high hyperchromicities, revealing strong secondary structuring of the single-stranded RNA. The more salt-resistant variants have still higher melting points and hyperchromicities. Single-stranded RNA melt a few degrees lower than double-strands of the same species, except for single-stranded MDV-1, which melts at the same temperature as its double-stranded form. Concomitant with increasing secondary structure of the single-stranded RNA is a decrease in their rates of annealing to form double strands. Single-stranded variants are both the immediate products of replication (replicas) and the preferred templates. SV-11 has 2 single-stranded RNA forms, only one of which is able to serve as an active template for Q.beta. replicase. Its inactive single-stranded form is more stable and apparently has a hairpin structure. The single-stranded RNA active in replication have vanishing electric dichroisms, indicating defined tertiary structures that do not allow an independent orientation of stems and loops in the electrical field.