Malavé Tania M, Forney James D
Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA.
Gene. 2004 Feb 4;326:97-105. doi: 10.1016/j.gene.2003.10.016.
Protein synthesis elongation factor 2 (eEF2) catalyzes the translocation of the peptidyl-tRNA from the A site to the P site of the ribosome. Most organisms encode a single EF2 protein and its activity is regulated by phosphorylation. We have identified a family of genes in Tetrahymena thermophila that encode proteins homologous to eEF2, yet are expressed only during sexual reproduction. These genes have been designated EFR for Elongation Factor 2 Related. EFR transcripts were not detected in vegetative cell cultures but rapidly increased about 6 h after the start of conjugation (mating). For comparison, we cloned, sequenced and analyzed the expression of the standard eEF2 gene from T. thermophila. Unlike EFR, transcripts from eEF2 were detected in vegetative cells but were present at lower concentrations during conjugation. Despite the high sequence identity between EFR and eEF2 from other organisms (about 42% at the amino acid level), key regulatory sequences that are involved in the regulation of eEF2 are altered in EFR. The sequence and expression data suggest that EFR is an eEF2 variant involved in a major translation regulatory mechanism that occurs during the formation of the macronuclear genome in conjugating cells.
蛋白质合成延伸因子2（eEF2）催化肽基-tRNA从核糖体的A位点转移至P位点。大多数生物体编码一种单一的EF2蛋白，其活性受磷酸化作用调控。我们在嗜热四膜虫中鉴定出一个基因家族，这些基因编码的蛋白与eEF2同源，但仅在有性生殖期间表达。这些基因被命名为EFR，即延伸因子2相关基因。在营养细胞培养物中未检测到EFR转录本，但在接合（交配）开始约6小时后迅速增加。作为比较，我们克隆、测序并分析了嗜热四膜虫标准eEF2基因的表达。与EFR不同，eEF2的转录本在营养细胞中可检测到，但在接合期间浓度较低。尽管EFR与其他生物体的eEF2之间具有高度的序列同一性（氨基酸水平约为42%），但参与eEF2调控的关键调控序列在EFR中发生了改变。序列和表达数据表明，EFR是一种eEF2变体，参与了接合细胞中大核基因组形成过程中发生的主要翻译调控机制。
