Shape and subunit organisation of the DNA methyltransferase M.AhdI by small-angle neutron scattering.
Shape and subunit organisation of the DNA methyltransferase M.AhdI by small-angle neutron scattering.
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DOI：
10.1016/j.jmb.2007.03.012
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发表时间：
2007-05-25
影响因子：
5.6
通讯作者：
Kneale, G. G.
中科院分区：
文献类型：
--
作者：
Callow, P.;Sukhodub, A.;Taylor, James E. N.;Kneale, G. G.
关键词：
I型限制-修饰（R-M）系统编码多亚基/多结构域酶。需要两个基因（M和S）来形成甲基转移酶（MTase），该甲基转移酶甲基化识别序列内的特定碱基并保护DNA免受内切核酸酶的切割。DNA甲基转移酶M.AhdI是化学计量为M2 S2的170 kDa四聚体，具有I型MTase的典型性质。已经用氘代S亚基制备了M.AhdI酶，以允许使用小角中子散射（SANS）方法的对比度变化。SANS数据收集在一些1H：2 H溶剂对比，以允许匹配的一个或其他的亚基的多亚基酶。多亚基酶中M亚基原位的回转半径（Rg）和最大尺寸（Dmax）（分别为50 μ m和190 μ m）与整个MTase的回转半径（Rg）和最大尺寸（Dmax）（分别为51 μ m和190 μ m）接近。相比之下，S亚基在原位具有实验确定的Rg = 35 μ g和Dmax = 110 μ g的值，表明它们在酶中更中心的位置。从头计算重建方法产生的M.AhdI的形状和亚基组织的低分辨率结构模型，其中的Z形结构的S亚基二聚体可以看出。相比之下，M亚基形成更细长和延伸的结构。MTase的核心包括两个S亚基和两个M亚基的球状区域，其中M亚基的延伸部分最有可能在外部末端形成高度移动的区域，当MTase结合时，该区域围绕DNA塌陷。
Type I restriction-modification (R-M) systems encode multisubunit/multidomain enzymes. Two genes (M and S) are required to form the methyltransferase (MTase) that methylates a specific base within the recognition sequence and protects DNA from cleavage by the endonuclease. The DNA methyltransferase M.AhdI is a 170 kDa tetramer with the stoichiometry M2S2 and has properties typical of a type I MTase. The M.AhdI enzyme has been prepared with deuterated S subunits, to allow contrast variation using small-angle neutron scattering (SANS) methods. The SANS data were collected in a number of 1H:2H solvent contrasts to allow matching of one or other of the subunits in the multisubunit enzyme. The radius of gyration (Rg) and maximum dimensions (Dmax) of the M subunits in situ in the multisubunit enzyme (50 Å and 190 Å, respectively) are close of those of the entire MTase (51 Å and 190 Å). In contrast, the S subunits in situ have experimentally determined values of Rg = 35 Å and Dmax = 110 Å, indicating their more central location in the enzyme. Ab initio reconstruction methods yield a low-resolution structural model of the shape and subunit organization of M.AhdI, in which the Z-shaped structure of the S subunit dimer can be discerned. In contrast, the M subunits form a much more elongated and extended structure. The core of the MTase comprises the two S subunits and the globular regions of the two M subunits, with the extended portion of the M subunits most probably forming highly mobile regions at the outer extremities, which collapse around the DNA when the MTase binds.
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影响因子：
1.6
作者：
Marks, P;McGeehan, J;Kneale, G
通讯作者：
Kneale, G
影响因子：
3.8
作者：
Powell, LM;Lejeune, E;Dryden, DTF
通讯作者：
Dryden, DTF
影响因子：
14.9
作者：
Janscak, P;Dryden, DTF;Firman, K
通讯作者：
Firman, K
DOI：
10.1073/pnas.0409851102
发表时间：
2005-03-01
影响因子：
11.1
作者：
Kim, JS;DeGiovanni, A;Kim, SH
通讯作者：
Kim, SH
影响因子：
3.4
作者：
Svergun, DI
通讯作者：
Svergun, DI