Bechtloff D, Grünenfelder B, Akerlund T, Nordström K
Department of Cell Biology, Biomedical Center, Uppsala University, S-751 24 Uppsala, Sweden.
J Bacteriol. 1999 Oct;181(20):6292-9. doi: 10.1128/JB.181.20.6292-6299.1999.
The aim of this study was to investigate whether the synthesis rates of some proteins change after the initiation of replication in Escherichia coli. An intR1 strain, in which chromosome replication is under the control of an R1 replicon integrated into an inactivated oriC, was used to synchronize chromosome replication, and the rates of protein synthesis were analyzed by two-dimensional polyacrylamide gel electrophoresis of pulse-labeled proteins. Computerized image analysis was used to search for proteins whose expression levels changed at least threefold after initiation of a single round of chromosome replication, which revealed 7 out of about 1,000 detected proteins. The various synthesis rates of three of these proteins turned out to be caused by unbalanced growth and the synthesis of one protein was suppressed in the intR1 strain. The rates of synthesis of the remaining three could be correlated only to the synchronous initiation of replication. These three proteins were analyzed by peptide mass mapping and appeared to be the products of the dps, gapA, and pyrI genes. Thus, the expression of the vast majority of proteins is not influenced by the state of chromosome replication, and a possible role of the replication-associated expression changes of the three identified proteins in the cell cycle is not clear.
本研究的目的是调查在大肠杆菌中复制起始后某些蛋白质的合成速率是否会发生变化。使用intR1菌株（其中染色体复制受整合到失活oriC中的R1复制子控制）来同步染色体复制，并通过脉冲标记蛋白质的二维聚丙烯酰胺凝胶电泳分析蛋白质合成速率。利用计算机图像分析来寻找在一轮染色体复制起始后表达水平至少变化三倍的蛋白质，结果在约1000种检测到的蛋白质中发现了7种。其中三种蛋白质的不同合成速率被证明是由生长不平衡导致的，并且有一种蛋白质在intR1菌株中的合成受到抑制。其余三种蛋白质的合成速率仅与复制的同步起始相关。通过肽质量图谱分析这三种蛋白质，发现它们似乎是dps、gapA和pyrI基因的产物。因此，绝大多数蛋白质的表达不受染色体复制状态的影响，并且这三种已鉴定蛋白质与复制相关的表达变化在细胞周期中的可能作用尚不清楚。
