Karyagina A S, Lunin V G, Degtyarenko K N, Uvarov V Y, Nikolskaya I I
Institute of Biological and Medical Chemistry, Moscow, Russia.
Gene. 1993 Feb 14;124(1):13-9. doi: 10.1016/0378-1119(93)90756-s.
A 2648-bp fragment from the P4 plasmid of Shigella sonnei strain 47 coding for the SsoII restriction endonuclease (ENase) and methyltransferase (MTase) (recognition sequence 5'-CCNGG) was sequenced. Two divergently arranged open reading frames of 905 bp for the SsoII ENase (R.SsoII) and 1137 bp for the MTase (M.SsoII) were identified. The coding regions are separated by 110 bp. The calculated M(r) of R.SsoII (35937) and M.SsoII (42887) are in good agreement with values previously obtained by in vitro transcription-translation experiments, i.e., 35 and 43 kDa for the ENase and MTase, respectively. The M.SsoII amino acid (aa) sequence revealed a considerable similarity to m5C-MTases recognizing the related sequences--M.EcoRII, M.dcm, M.MspI, M.BsuFI, M.HpaII, and M.HhaI. Surprisingly, the greatest degree of homology has been observed between the aa sequences of M.SsoII and M.NlaX, with an unidentified recognition sequence. The multiple alignment of aa sequences helps to identify the blocks of conserved aa in variable regions of MTases. These conserved aa can play a key role in target recognition. Some aspects of evolution of m5C-MTases are discussed.
对宋内志贺氏菌47菌株P4质粒上一段2648 bp的片段进行了测序，该片段编码SsoII限制性内切酶（ENase）和甲基转移酶（MTase）（识别序列为5'-CCNGG）。鉴定出两个反向排列的开放阅读框，分别为905 bp的SsoII ENase（R.SsoII）和1137 bp的MTase（M.SsoII）。编码区由110 bp隔开。计算得到的R.SsoII（35937）和M.SsoII（42887）的M(r)与先前通过体外转录-翻译实验获得的值高度一致，即ENase和MTase的分子量分别为35 kDa和43 kDa。M.SsoII氨基酸（aa）序列与识别相关序列的m5C-MTases（M.EcoRII、M.dcm、M.MspI、M.BsuFI、M.HpaII和M.HhaI）有相当大的相似性。令人惊讶的是，在M.SsoII和M.NlaX的aa序列之间观察到最大程度的同源性，M.NlaX的识别序列未知。aa序列的多重比对有助于识别MTases可变区域中保守aa的区域。这些保守aa在靶标识别中可能起关键作用。讨论了m5C-MTases进化的一些方面。
