痘苗病毒天坛株基因组病毒生长因子基因结构的研究

克隆了位于我国痘苗病毒天坛株基因组左端的病毒生长因子（ＶＧＦ）基因并对其编码多肽的结构特点进行了分析。结果表明，由天坛株ＶＧＦ基因所推导的氨基酸序列具有典型的上皮生长因子（ＥＧＦ）超家族成员的特征序列和结构特点，在核苷酸及氨基酸水平上天坛株ＶＧＦ与其他正痘病毒ＶＧＦ的同源性在８５％～９５％之间，氨基酸残基的缺失和插入等变异主要集中出现在多肽的信号肽和穿膜区，推测对功能的影响不大。此外，我们发现由天坛株基因组右末端的开放读码框架（ＯＲＦ）ＴＢ２２Ｌ推导的氨基酸序列与天坛株ＶＧＦ多肽第６７位至１４０位完全相同，提示ＯＲＦＴＢ２２Ｌ可能是天坛株基因组第二个ＶＧＦ基因的变异产物。

Characteristics of virus growth factor (VGF) encoded by vaccinia virus Tian Tan strain

Vaccinia virus growth factor (VGF) is encoded by an early gene located near the border between the terminal inverted repeats and the internal unique region of the viral genome. It has been suggested that secreted VGF may serve to stimulate the metabolism of neighboring uninfected cells, thereby increasing the capacity of these cells to support viral replication. In this study, we cloned and sequenced the VGF gene of vaccinia virus strain Tian Tan. The analytical results indicated that VGF of strain Tian Tan possessed the core sequences of Epidermal growth factor superfamily, and more closely related to that of strain WR than to those of other orthopoxvirus strains. Overall deduced amino acid divergence of 4.3% was observed between Tian Tan and WR VGF protein, while divergences ranged from 10% to 20% compared to other orthopoxviruses strains. Most of the amino acid substitutions were found within signal peptide and transmembrane regions, but were not present in secreted ligand domain. It was striking that the amino acid sequence deduced from the ORF TB22L which located within the right terminal region of genome was identical to VGF protein amino acids 67-140, suggesting that ORF TB22L may be derived from the seconed copy of VGF gene of strain Tian Tan.