Rizvi Irum, Choudhury Nirupam Roy, Tuteja Narendra
Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, 110067, India.
Protoplasma. 2016 Mar;253(2):467-75. doi: 10.1007/s00709-015-0825-2. Epub 2015 May 6.
Minichromosome maintenance 2-7 (MCM2-7) proteins are conserved eukaryotic replicative factors essential for the DNA replication at its initiation and elongation step, and act as a licensing factor. The MCM2-7 and MCM4/6/7subcomplex exhibit DNA helicase activity, and are therefore regarded as the replicative helicase. The MCM proteins have not been studied in detail in plant system. Here, we present the biochemical characterization of Arabidopsis thaliana MCM3 single subunit and show that it exhibits in vitro unwinding and ATPase activities. AtMCM3 shows a greater unwinding activity with 5' forked partial DNA duplex substrate as compared to 3' forked and non-forked substrates. ATP and magnesium ion are indispensable for its DNA helicase activity. Specifically, ATP and dATP are the preferred nucleotides for its unwinding activity. The directionality of the AtMCM3 has been determined to be in 3' to 5' direction. The oligomerization status of AtMCM3 single subunit protein indicates that it is present in different multimeric forms. The unraveling of the helicase activity of AtMCM3 will provide better insights into the plant DNA replication.
微小染色体维持蛋白2 - 7（MCM2 - 7）是保守的真核生物复制因子，在DNA复制的起始和延伸步骤中必不可少，并作为一种许可因子发挥作用。MCM2 - 7和MCM4/6/7亚复合体具有DNA解旋酶活性，因此被视为复制性解旋酶。MCM蛋白在植物系统中尚未得到详细研究。在此，我们展示了拟南芥MCM3单亚基的生化特性，并表明它在体外具有解旋和ATP酶活性。与3' 叉状和非叉状底物相比，AtMCM3对5' 叉状部分DNA双链底物表现出更高的解旋活性。ATP和镁离子对其DNA解旋酶活性不可或缺。具体而言，ATP和dATP是其解旋活性的首选核苷酸。已确定AtMCM3的方向性为3' 到5' 方向。AtMCM3单亚基蛋白的寡聚化状态表明它以不同的多聚体形式存在。AtMCM3解旋酶活性的揭示将为植物DNA复制提供更好的见解。
