Hwang Jisub, Park Sun-Ha, Lee Chang Woo, Do Hackwon, Shin Seung Chul, Kim Han-Woo, Lee Sung Gu, Park Hyun Ho, Kwon Sunghark, Lee Jun Hyuck
Research Unit of Cryogenic Novel Material, Korea Polar Research Institute, Incheon 21990, Republic of Korea.
Department of Polar Sciences, University of Science and Technology, Incheon 21990, Republic of Korea.
IUCrJ. 2021 Sep 1;8(Pt 5):842-852. doi: 10.1107/S2052252521005704.
MarR family proteins regulate the transcription of multiple antibiotic-resistance genes and are widely found in bacteria and archaea. Recently, a new MarR family gene was identified by genome analysis of the psychrophilic bacterium sp. TG-14, which was isolated from sediment-laden basal ice in Antarctica. In this study, the crystal structure of the MarR protein from sp. TG-14 (MarR) was determined at 1.6 Å resolution. In the crystal structure, a novel lipid-type compound (palmitic acid) was found in a deep cavity, which was assumed to be an effector-binding site. Comparative structural analysis of homologous MarR family proteins from a mesophile and a hyperthermophile showed that the DNA-binding domain of MarR exhibited relatively high mobility, with a disordered region between the β1 and β2 strands. In addition, structural comparison with other homologous complex structures suggests that this structure constitutes a conformer transformed by palmitic acid. Biochemical analysis also demonstrated that MarR binds to cognate DNA, where MarR is known to recognize two putative binding sites depending on its molar concentration, indicating that MarR binds to its cognate DNA in a stoichiometric manner. The present study provides structural information on the cold-adaptive MarR protein with an aliphatic compound as its putative effector, extending the scope of MarR family protein research.
MarR家族蛋白调控多种抗生素抗性基因的转录，广泛存在于细菌和古菌中。最近，通过对从南极洲富含沉积物的底部冰层中分离出的嗜冷细菌TG-14菌株进行基因组分析，鉴定出一个新的MarR家族基因。在本研究中，测定了TG-14菌株的MarR蛋白（MarR）的晶体结构，分辨率为1.6 Å。在晶体结构中，在一个深腔内发现了一种新型脂质类化合物（棕榈酸），该腔被认为是效应物结合位点。对来自嗜温菌和嗜热菌的同源MarR家族蛋白进行比较结构分析表明，MarR的DNA结合结构域表现出相对较高的流动性，在β1和β2链之间有一个无序区域。此外，与其他同源复合物结构的结构比较表明，该结构构成了由棕榈酸转化的构象异构体。生化分析还表明，MarR与同源DNA结合，已知MarR根据其摩尔浓度识别两个假定的结合位点，这表明MarR以化学计量方式与其同源DNA结合。本研究提供了以脂肪族化合物作为假定效应物的冷适应性MarR蛋白的结构信息，扩展了MarR家族蛋白的研究范围。
