Kishore Anita I, Mayer Michael R, Prestegard James H
Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602-4712, USA.
Nucleic Acids Res. 2005 Oct 27;33(18):e164. doi: 10.1093/nar/gni165.
Analysis of the 13C isotopic labeling patterns of nucleoside monophosphates (NMPs) extracted from Escherichia coli grown in a mixture of C-1 and C-2 glucose is presented. By comparing our results to previous observations on amino acids grown in similar media, we have been able to rationalize the labeling pattern based on the well-known biochemistry of nucleotide biosynthesis. Except for a few notable absences of label (C4 in purines and C3' in ribose) and one highly enriched site (C1' in ribose), most carbons are randomly enriched at a low level (an average of 13%). These sparsely labeled NMPs give less complex NMR spectra than their fully isotopically labeled analogs due to the elimination of most 13C-13C scalar couplings. The spectral simplicity is particularly advantageous when working in ordered systems, as illustrated with guanosine diphosphate (GDP) bound to ADP ribosylation factor 1 (ARF1) aligned in a liquid crystalline medium. In this system, the absence of scalar couplings and additional long-range dipolar couplings significantly enhances signal to noise and resolution.
本文介绍了对从在C-1和C-2葡萄糖混合物中生长的大肠杆菌中提取的单磷酸核苷（NMP）的13C同位素标记模式的分析。通过将我们的结果与之前在类似培养基中生长的氨基酸的观察结果进行比较，我们能够根据核苷酸生物合成的著名生物化学原理来解释标记模式。除了一些明显没有标记的位点（嘌呤中的C4和核糖中的C3'）和一个高度富集的位点（核糖中的C1'）外，大多数碳原子以低水平随机富集（平均为13%）。由于消除了大多数13C-13C标量耦合，这些稀疏标记的NMP比其完全同位素标记的类似物具有更简单的NMR光谱。当在有序系统中工作时，光谱的简单性特别有利，如结合到在液晶介质中排列的ADP核糖基化因子1（ARF1）上的二磷酸鸟苷（GDP）所示。在这个系统中，标量耦合和额外的远程偶极耦合的缺失显著提高了信噪比和分辨率。
