Wohlgemuth Ingo, Beringer Malte, Rodnina Marina V
Institute of Physical Biochemistry, University of Witten/Herdecke, Stockumer Strasse 10, 58448 Witten, Germany.
EMBO Rep. 2006 Jul;7(7):699-703. doi: 10.1038/sj.embor.7400732. Epub 2006 Jun 16.
The catalytic site of the ribosome, the peptidyl transferase centre, is located on the large (50S in bacteria) ribosomal subunit. On the basis of results obtained with small substrate analogues, isolated 50S subunits seem to be less active in peptide bond formation than 70S ribosomes by several orders of magnitude, suggesting that the reaction mechanisms on 50S subunits and 70S ribosomes may be different. Here we show that with full-size fMet-tRNA(fMet) and puromycin or C-puromycin as peptide donor and acceptor substrates, respectively, the reaction proceeds as rapidly on 50S subunits as on 70S ribosomes, indicating that the intrinsic activity of 50S subunits is not different from that of 70S ribosomes. The faster reaction on 50S subunits with fMet-tRNA(fMet), compared with oligonucleotide substrate analogues, suggests that full-size transfer RNA in the P site is important for maintaining the active conformation of the peptidyl transferase centre.
核糖体的催化位点，即肽基转移酶中心，位于核糖体大亚基（细菌中为50S）上。根据使用小底物类似物获得的结果，分离出的50S亚基在肽键形成中的活性似乎比70S核糖体低几个数量级，这表明50S亚基和70S核糖体上的反应机制可能不同。在此我们表明，分别以全长甲硫氨酰 - tRNA（fMet）和嘌呤霉素或C - 嘌呤霉素作为肽供体和受体底物时，50S亚基上的反应与70S核糖体上的反应一样迅速，这表明50S亚基的内在活性与70S核糖体的内在活性并无差异。与寡核苷酸底物类似物相比，50S亚基与fMet - tRNA（fMet）反应更快，这表明P位点的全长转移RNA对于维持肽基转移酶中心的活性构象很重要。
