Newberry V, Yaguchi M, Garrett R A
Eur J Biochem. 1977 Jun 1;76(1):51-61. doi: 10.1111/j.1432-1033.1977.tb11569.x.
A fragment of ribosomal protein S4 was prepared by limited trypsin degestion of a specific complex between protein S4 and 16-S RNA. It was characterised for amino acid sequence and the N-terminal 46 amino acids were found to be absent. An intermediate fragment, cut at Arg-43, was also observed at low trypsin concentrations. Evidence is presented that the protected fragment constitutes the primary RNA-binding region of the protein. No smaller protein fragments were found that rebound to the RNA. A mechanism for the degradation of the N-terminal region of the protein is proposed and two probable functions of the excised region are given. Under milder trypsin digestion conditions than for the complex, the same fragment, cut at Arg-46, was also prepared from the free protein. This result, together with that from a control experiment, indicates that at least within this local region, the protein conformation is conserved in both the free protein and the protein-RNA complex. This is the first direct evidence for the conservation of conformation in a protein when both complexed and uncomplexed with a ribosomal RNA.
通过对核糖体蛋白S4与16 - S RNA的特定复合物进行有限的胰蛋白酶消化制备了核糖体蛋白S4的一个片段。对其氨基酸序列进行了表征，发现N端的46个氨基酸缺失。在低胰蛋白酶浓度下还观察到了在Arg - 43处切割的中间片段。有证据表明受保护的片段构成了该蛋白的主要RNA结合区域。未发现能与RNA重新结合的更小的蛋白片段。提出了该蛋白N端区域的降解机制，并给出了切除区域的两种可能功能。在比复合物更温和的胰蛋白酶消化条件下，也从游离蛋白制备了在Arg - 46处切割的相同片段。这一结果与对照实验的结果一起表明，至少在这个局部区域内，游离蛋白和蛋白 - RNA复合物中的蛋白构象是保守的。这是蛋白质在与核糖体RNA结合和未结合时构象保守的首个直接证据。
