XmnI 限制-修饰系统：克隆、表达、序列组织以及 R 基因与 M 基因之间的相似性

The XmnI restriction-modification system: cloning, expression, sequence organization and similarity between the R and M genes.

作者信息

Nwankwo D O, Lynch J J, Moran L S, Fomenkov A, Slatko B E

机构信息

New England Biolabs, Inc., Beverly, MA 01915, USA.

出版信息

Gene. 1996 Sep 16;173(2):121-7. doi: 10.1016/0378-1119(96)00062-5.

DOI:10.1016/0378-1119(96)00062-5

PMID:8964488

Abstract

The xmnIRM genes from Xanthomonas manihotis 7AS1 have been cloned and expressed in Escherichia coli. The nucleotide (nt) sequences of both genes were determined. The XmnI methyltransferase (MTase)-encoding gene is 1861 bp in length and codes for 620 amino acids (aa) (68660 Da). The restriction endonuclease (ENase)-encoding gene is 959 bp long and therefore codes for a 319-aa protein (35275 Da). The two genes are aligned tail to tail and they overlap at their respective stop codons About 4 x 10(4) units/g wet cell paste of R.XmnI was obtained following IPTG induction in a suitable E. coli host. The xmnIR gene is expressed from the T7 promoter. M.XmnI probably modifies the first A in the sequence, GAA(N)4TTC. The xmnIR and M genes contain regions of conserved similarity and probably evolved from a common ancestor. M.XmnI is loosely related to M.EcoRI. The XmnI R-M system and the type-I R-M systems probably derived from a common ancestor.

摘要

来自木薯黄单胞菌7AS1的xmnIRM基因已被克隆并在大肠杆菌中表达。测定了这两个基因的核苷酸（nt）序列。编码XmnI甲基转移酶（MTase）的基因长度为1861 bp，编码620个氨基酸（aa）（68660 Da）。编码限制性内切酶（ENase）的基因长959 bp，因此编码一个319 aa的蛋白质（35275 Da）。这两个基因尾对尾排列，在各自的终止密码子处重叠。在合适的大肠杆菌宿主中经IPTG诱导后，每克湿细胞糊可获得约4×10⁴单位的R.XmnI。xmnIR基因由T7启动子表达。M.XmnI可能修饰序列GAA(N)₄TTC中的第一个A。xmnIR和M基因包含保守相似区域，可能起源于共同祖先。M.XmnI与M.EcoRI关系松散。XmnI R-M系统和I型R-M系统可能起源于共同祖先。