THE SIZE DISTRIBUTIONS OF PROTEINS, MESSENGER-RNA AND NUCLEAR-RNA
THE SIZE DISTRIBUTIONS OF PROTEINS, MESSENGER-RNA AND NUCLEAR-RNA
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DOI：
10.1007/bf01732582
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发表时间：
1980-01-01
影响因子：
3.9
通讯作者：
COHEN, JE
中科院分区：
文献类型：
--
作者：
SOMMER, SS;COHEN, JE
大小（分子量）和亚基数量的频率分布是根据 500 多种哺乳动物和细菌蛋白质的列表确定的。多肽的大小分布通过对数正态分布很好地拟合，中值约为40,000道尔顿，偏差为1.8。大约 60% 的蛋白质以多聚体形式存在。在多聚体中，75% 具有两个或四个亚基，而不到 1% 的多聚体具有大于三个的奇数个亚基。超过 90% 的情况下，给定的多聚体由大小几乎相等的亚基组成，因此 N 聚体的大小呈对数正态分布，中值为 N x 40,000 道尔顿，偏差为 1.8。哺乳动物和细菌蛋白以及细胞内和细胞外蛋白的多肽大小和亚基数量的分布相似。HeLa 和 CHO 细胞 mRNA 的沉降曲线表明，哺乳动物 mRNA 的长度呈对数正态分布，中值为 1.4 kb，偏差为 2.0。这意味着，平均而言，mRNA 种类仅比其编码的成熟多肽大 25% 左右。因此，最多一小部分哺乳动物 mRNA 可以编码大的前体多肽，然后将其切割成许多成熟的多肽（如脊髓灰质炎 mRNA），或者编码 3' 共端 mRNA，其中较大的物种包含多达四种蛋白质的信息（如腺病毒 mRNA）。来自 HeLa 的新生核 RNA 的沉降谱表明，转录单位的长度分布有 2 个组成部分：一个以 10-15 的半长衰减的指数组成部分kb，并且非常短的分子的频率很高。然而，如果发生以下一种或多种情况，转录单位长度的其他分布（例如对数正态分布）也可能与数据一致：新生链的生理裂解、放线菌素 D 对非 rRNA 转录的扰动或分离过程中的降解。标记 60 分钟的 HeLa 核 RNA 的长度分布与新生核 RNA 的长度分布相似，表明完整的 hnRNA 链在被标记后很快被转运或降解。劈开的。
The frequency distributions of size (molecular weight) and of numbers of subunits were determined from lists of over 500 mammalian and bacterial proteins. The size distribution of polypeptides is well fitted by a lognormal distribution with a median value of about 40,000 daltons and a deviation of 1.8. About 60% of all proteins exist in multimeric aggregates. Of the multimers 75% have either two or four subunits while less than 1% have an odd number of subunits that is greater than three. Over 90% of the time, a given multimer is composed of subunits of nearly equal size so that the size of a N-mer is lognormally distributed with a median value of N x 40,000 daltons and a deviation of 1.8. The distribution of polypeptide size and subunit number is similar for mammalian and bacterial proteins as well as for intracellular and extracellular proteins.The sedimentation profiles of mRNA from HeLa and CHO cells indicate that the lengths of mammalian mRNA are lognormally distributed with a median value of 1.4 kb and a deviation of 2.0. This implies that, on the average, a mRNA species is only about 25% larger than the mature polypeptide it codes for. Therefore, at most a small fraction of mammalian mRNA could code for large precursor polypeptides which are then cleaved into a number of mature polypeptides (like polio mRNA), or for 3′ coterminal mRNAs where the larger species contain the information for up to four proteins (like adenovirus mRNA).The sedimentation profile of nascent nuclear RNA from HeLa suggests that the length distribution of transcription units has 2 components: An exponential component that decays with a half-length of 10–15 kb, and a high frequency of very short molecules. However, other distributions (for example, the lognormal distribution) of transcription unit lengths could also be consistent with the data if one or more of the following occurred: Physiological cleavage of nascent chains, perturbation of non-rRNA transcription by actinomycin D, or degradation during isolation.The length distribution of HeLa nuclear RNA labeled for 60 min is similar to that of nascent nuclear RNA, indicating that a completed hnRNA chain is quickly transported or degraded after being cleaved.