Elliott R M, Davison A N, Lim L
Biochem J. 1980 Jul 15;190(1):215-23. doi: 10.1042/bj1900215.
A study has been made of the developmental changes that occur in the RNA and protein moieties of mRNA-protein particles isolated from newborn and adult rat forebrain free polyribosomes. mRNA-protein particles were isolated by oligo(dT)-cellulose chromatography from salt-washed polyribosomes dissociated by puromycin/0.5 M-KCl treatment as two fractions (E1 and E2) by using Tris/HCl/NaCl eluting buffers containing respectively 25 and 50% (v/v) formamide. Isopycnic centrifugation on CsCl gradients showed that the newborn-derived fractions E1 and E2 has buoyant densities of 1.48--1.50 and 1.41--1.43 g/cm3. Adult-derived E1 and E2 fractions had corresponding values of 1.47 and 1.42 g/cm3. The pooled mRNA-protein particles from the E1 and E2 fractions after deproteinization with proteinase K sedimented with a mean size of approx. 18 S on a sucrose gradient containing 85% formamide with little differences between mRNA molecules from newborn and adult. The mean lengths of the poly(A) segments were similar, being about 130 nucleotides long. Distinct changes were found in the protein composition of the mRNA-protein particles. Fractions E1 and E2 from the newborn contained two major proteins of mol.wts. 74 000 and 52 000 with differences in the relative proportions in each fraction. In contrast, adult fractions E1 and E2 contained predominantly the larger protein. However, the adult fraction E2 contained a more heterogeneous population of minor bands of proteins, including that of mol.wt. 52 000. The findings are discussed briefly in relation to other changes in the developing brain.
对从新生和成年大鼠前脑游离多核糖体中分离出的mRNA-蛋白质颗粒的RNA和蛋白质部分所发生的发育变化进行了研究。通过寡聚（dT）-纤维素色谱法，从经嘌呤霉素/0.5M-KCl处理解离的盐洗多核糖体中分离出mRNA-蛋白质颗粒，使用分别含有25%和50%（v/v）甲酰胺的Tris/HCl/NaCl洗脱缓冲液将其分为两个组分（E1和E2）。在CsCl梯度上进行等密度离心表明，新生大鼠来源的组分E1和E2的浮力密度分别为1.48--1.50 g/cm³和1.41--1.43 g/cm³。成年大鼠来源的E1和E2组分的相应值分别为1.47 g/cm³和1.42 g/cm³。用蛋白酶K脱蛋白后，将E1和E2组分合并的mRNA-蛋白质颗粒在含有85%甲酰胺的蔗糖梯度上沉降，平均大小约为18S，新生和成年大鼠的mRNA分子之间差异不大。多聚（A）片段的平均长度相似，约为130个核苷酸长。在mRNA-蛋白质颗粒的蛋白质组成中发现了明显变化。新生大鼠的E1和E2组分包含两种主要蛋白质，分子量分别为74000和52000，每个组分中相对比例不同。相比之下，成年大鼠的E1和E2组分主要含有较大的蛋白质。然而，成年大鼠的E2组分包含更异质的次要蛋白质条带群体, 包括分子量为52000的蛋白质。结合发育中大脑的其他变化简要讨论了这些发现。
