Kim Sulhee, Lee Kitaik, Park Sun-Ha, Kwak Geun-Hee, Kim Min Seok, Kim Hwa-Young, Hwang Kwang Yeon
Department of Biotechnology, Korea University, Seoul 02841, Korea.
Department of Biochemistry and Molecular Biology, Yeungnam University College of Medicine, Daegu 42415, Korea.
Antioxidants (Basel). 2021 Mar 5;10(3):389. doi: 10.3390/antiox10030389.
Methionine sulfoxide reductase (Msr) is a family of enzymes that reduces oxidized methionine and plays an important role in the survival of bacteria under oxidative stress conditions. MsrA and MsrB exist in a fusion protein form (MsrAB) in some pathogenic bacteria, such as (), , and . To understand the fused form instead of the separated enzyme at the molecular level, we determined the crystal structure of MsrAB at 2.2 Å, which showed that a linker region (, 193-205) between two domains interacted with each MsrA or MsrB domain via three salt bridges (E193-K107, D197-R103, and K200-D339). Two acetate molecules in the active site pocket showed an planar electron density map in the crystal structure, which interacted with the conserved residues in fusion MsrABs from the pathogen. Biochemical and kinetic analyses revealed that is required to increase the catalytic efficiency of MsrAB. Two salt bridge mutants (D193A and E199A) were located at the entrance or tailgate of . Therefore, the linker region of the MsrAB fusion enzyme plays a key role in the structural stability and catalytic efficiency and provides a better understanding of why MsrAB exists in a fused form.
甲硫氨酸亚砜还原酶（Msr）是一类可还原氧化型甲硫氨酸的酶家族，在细菌于氧化应激条件下的存活中发挥重要作用。在一些病原菌中，如（）、（）和（），MsrA和MsrB以融合蛋白形式（MsrAB）存在。为了在分子水平上理解这种融合形式而非分离的酶，我们测定了MsrAB在2.2 Å分辨率下的晶体结构，结果表明两个结构域之间的连接区（，193 - 205）通过三个盐桥（E193 - K107、D197 - R103和K200 - D339）与每个MsrA或MsrB结构域相互作用。活性位点口袋中的两个乙酸分子在晶体结构中显示出平面电子密度图，它们与来自病原体的融合MsrAB中的保守残基相互作用。生化和动力学分析表明，（）是提高MsrAB催化效率所必需的。两个盐桥突变体（D193A和E199A）位于（）的入口或后挡板处。因此，MsrAB融合酶的连接区在结构稳定性和催化效率中起关键作用，并有助于更好地理解MsrAB为何以融合形式存在。
