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首页> 外文期刊>Molecular and Cellular Biology >The core proteins A2 and B1 exist as (A2)3B1 tetramers in 40S nuclear ribonucleoprotein particles.
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The core proteins A2 and B1 exist as (A2)3B1 tetramers in 40S nuclear ribonucleoprotein particles.

机译：核心蛋白A2和B1以（A2）3B1四聚体的形式存在于40S核糖核蛋白颗粒中。

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The six "core" proteins of HeLa cell 40S nuclear ribonucleoprotein particles (hnRNP particles) package 700-nucleotide lengths of pre-mRNA into a repeating array of regular particles. We have previously shown that the C proteins exist as anisotropic tetramers of (C1)3C2 in 40S hnRNP particles and that each particle probably contains three such tetramers. We report here that proteins A2 and B1 also exist in monoparticles as (A2)3B1 tetramers and that each monoparticle contains at least three such tetramers. Proteins A2 and B1 dissociate from isolated monoparticles as a stable tetramer upon nuclease digestion. In low-salt gradients, the tetramers sediment at 6.8S, which is consistent with a mass of 145 kDa. In 200 mM salt, the concentration which dissociates these proteins from RNA, only 4.2S dimers exist in solution. Tetramers of (A2)3B1 possess the ability to package multiples of 700 nucleotides of RNA in vitro into an array of regular, 22.5-nm 43S particles. Unlike the in vitro assembly of intact 40S hnRNP, the (A2)3B1 tetramers assemble by means of a highly cooperative process. These findings indicate that the (A2)3B1 tetramers play a major role in hnRNP assembly and they further support the contention that 40S monoparticles are regular structures composed of three copies of three different tetramers, i.e., 3[(A1)3B2, (A2)3B1, (C1)3C2].
机译：HeLa细胞40S核糖核蛋白颗粒（hnRNP颗粒）的六个“核心”蛋白将700个核苷酸长的pre-mRNA包装成重复的规则颗粒阵列。先前我们已经表明，C蛋白以（C1）3C2的各向异性四聚体形式存在于40S hnRNP颗粒中，并且每个颗粒可能都包含三个这样的四聚体。我们在此报告蛋白质A2和B1也以（A2）3B1四聚体的形式存在于单颗粒中，并且每个单颗粒均包含至少三个这样的四聚体。核酸酶消化后，蛋白质A2和B1作为稳定的四聚体从分离的单颗粒中解离。在低盐梯度中，四聚体在6.8S处沉积，这与145 kDa的质量一致。在200 mM的盐中，这些蛋白质与RNA分离的浓度中，溶液中仅存在4.2S二聚体。 （A2）3B1的四聚体具有将体外700个核苷酸的倍数包装成规则的22.5 nm 43S颗粒阵列的能力。与完整的40S hnRNP的体外组装不同，（A2）3B1四聚体通过高度协作的过程进行组装。这些发现表明，（A2）3B1四聚体在hnRNP组装中起主要作用，它们进一步支持以下观点：40S单颗粒是由三个不同的四聚体的三个副本组成的规则结构，即3 [（（A1）3B2，（A2） 3B1，（C1）3C2]。

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