Koonin E V, Ilyina T V
Institute of Microbiology, Academy of Sciences, Moscow, Russia.
J Gen Virol. 1992 Oct;73 ( Pt 10):2763-6. doi: 10.1099/0022-1317-73-10-2763.
It is demonstrated, by means of computer-assisted analysis, that C1 protein involved in the replication of geminivirus DNA is related to the rolling circle replication initiator proteins of eubacterial plasmids, particularly the plasmids of the pMV158 family. Three sequence motifs conserved in the geminivirus and plasmid replication proteins were delineated, one of them encompassing the Tyr residue that presumably forms a covalent linkage to DNA. These findings are compatible with the results of recent analyses of geminivirus replicative intermediates suggesting a rolling circle mechanism for geminivirus DNA replication. It is hypothesized that C1 protein initiates the rolling circle replication of geminivirus DNA by nicking a specific site in the virus-sense DNA and covalently linking to the 5' side of the nick. The putative rolling circle replication initiator domain comprises the N-terminal portion of C1, whereas its C-terminal part is a putative helicase domain. By analogy with prokaryotic systems, it is speculated that the replication initiator domain and the helicase domain function coordinately. The possibility of the origin of geminiviruses from prokaryotic circular ssDNA replicons is discussed.
通过计算机辅助分析表明，参与双生病毒DNA复制的C1蛋白与真细菌质粒，特别是pMV158家族质粒的滚环复制起始蛋白相关。确定了双生病毒和质粒复制蛋白中保守的三个序列基序，其中一个基序包含可能与DNA形成共价连接的酪氨酸残基。这些发现与最近对双生病毒复制中间体的分析结果一致，表明双生病毒DNA复制采用滚环机制。据推测，C1蛋白通过在病毒链DNA的特定位点切口并与切口的5'端共价连接，启动双生病毒DNA的滚环复制。推定的滚环复制起始结构域包括C1的N端部分，而其C端部分是推定的解旋酶结构域。类比原核系统推测，复制起始结构域和解旋酶结构域协同发挥功能。还讨论了双生病毒起源于原核环状单链DNA复制子的可能性。
