Epstein-Barr病毒基因组编码的BARF-1和EC-LF4蛋白质与免疫球蛋白结构同源

将EB病毒蛋白质BARF-1和EC-LF4与NBRF蛋白质库的序列进行局部同源性检索以及与已知的Ig V或C功能区相关分子进行对准比较,检查了同源性积分的统计学意义,并进行了二级结构预测和疏水性分析,确定了BARF-1的第13-124位和第126-221位残基片段分别与V和C样功能区类似,EC-LF4的第20-135位残基片段与V样功能区相似,BARF-1是非膜蛋白,EC-LF4是膜整合蛋白,其胞外部分近膜侧有一个类似于Ig绞链区的序列。因此,BARF-1与Ig轻链结构相似,EC-LF4与CD8抗原的第一条链相似。根据Ig超族分子的一般功能(即介导细胞粘附和细胞识别),推测EC-LF4可能作为一种粘附分子与淋巴细胞表面的Ig相关分子结合而促进EB病毒对淋巴细胞的感染。BARF-1因已知与病毒复制有关,与Ig超族的一般功能无关。EC-LF4和BARF-1的Ig样功能区可能来源于EB病毒对宿主细胞Ig基因的整合。

BARF-1 and EC-LF4 encoded by the Epstein-Barr virus genome are Structurally Homologous With Immunogolobulin

Local homology searches for Epstein-Barr virus (EBV)-encoded proteins BARF-1 and EC-LF4 with sequences in the NBRF database were performed. Comparisons between the two EBV proteins and some Ig-related molecules were made. The statistical significance of homology scores were checked and secondary structures of BARF-1 and EC-LF4 were predicted. All these extensive analyses confirm that BARF-1 has one Ig-V and one C related regions and EC-LF4 has one V-related region. The membrane-propoximal extracytoplasmic part of the EC-LF4 molecule has a sequence akin to Ig hinge regions. In the general architecture, BARF-1 is like an Ig light chain and EC-LF4 like CD8 chain I in structure. Since the general function of Ig-superfamily members is to mediate cell adhesion and cell recognition, we proposed that EC-LF4 may be an adhesion molecule able to bind with Ig-related mole- cules on the lymphocyte surface thus to increase the infectivity of EB virus. BARF-1 which is known to be involved in the virus replication, may have nothing to do with the functions of the Ig superfamily. The Ig-like domains of the two virus proteins may be derived from the integration of the host gene into the Ig virus' genome during EBV infection.