Choi K M, Atkins J F, Gesteland R F, Brimacombe R
Max-Planck-Institut für Molekulare Genetik, Berlin, Germany.
Eur J Biochem. 1998 Jul 15;255(2):409-13. doi: 10.1046/j.1432-1327.1998.2550409.x.
The ribosomal environment of the N-terminus of the nascent polypeptide chain has been investigated using peptides of different lengths, synthesized in situ on Escherichia coli ribosomes; the peptides each carry a photoreactive diazirine moiety at their N-terminus, so as to generate cross-links to neighbouring ribosomal components. Our previous studies [Choi, K. M. & Brimacombe, R. (1998) Nucleic Acids Res. 26, 887-895] with three independent families of peptides, derived from the E. coli ompA protein gene, the tetracycline-resistance gene and the bacteriophage T4 gene 60, identified a series of sites within the 23S rRNA to which the peptides became cross-linked. The distribution of these cross-links indicated that the nascent peptide is very flexible within the 50S subunit. Here, we demonstrate that the N-termini of the ompA and gene-60 peptides can, in addition, even become concomitantly cross-linked to the 30S subunit. The cross-linking is predominantly to 30S ribosomal proteins S1, S2, S4 and (to a lesser extent) S3, which form a cluster near to the decoding region. This result is discussed in terms of the flexibility of the nascent peptide during the co-translational folding process, and in terms of the 'ribosomal bypass' phenomenon which is known to occur during translation of the gene 60 mRNA.
利用在大肠杆菌核糖体上原位合成的不同长度的肽，对新生多肽链N端的核糖体环境进行了研究；这些肽在其N端均带有一个光反应性重氮环丙烷部分，以便与相邻的核糖体组分产生交联。我们之前的研究[Choi, K. M. & Brimacombe, R. (1998) Nucleic Acids Res. 26, 887 - 895]使用了源自大肠杆菌ompA蛋白基因、四环素抗性基因和噬菌体T4基因60的三个独立肽家族，确定了23S rRNA内一系列肽与之发生交联的位点。这些交联的分布表明新生肽在50S亚基内非常灵活。在此，我们证明ompA和基因60肽的N端此外甚至可以同时与30S亚基发生交联。交联主要发生在30S核糖体蛋白S1、S2、S4以及（程度较轻的）S3上，它们在解码区域附近形成一个簇。根据新生肽在共翻译折叠过程中的灵活性以及已知在基因60 mRNA翻译过程中发生的“核糖体跳跃”现象对这一结果进行了讨论。
