Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, 10326, Republic of Korea.
Structural Biology Lab, B2SBIO, Yeonsu-gu, Incheon, Republic of Korea.
Sci Rep. 2020 Dec 3;10(1):21039. doi: 10.1038/s41598-020-78148-x.
The niacin-responsive repressor, NiaR, is transcriptional repressor of certain nicotinamide adenine dinucleotide (NAD) biosynthetic genes in response to an increase in niacin levels. NAD is a vital molecule involved in various cellular redox reactions as an electron donor or electron acceptor. The NiaR family is conserved broadly in the Bacillus/Clostridium group, as well as in the Fusobacteria and Thermotogales lineages. The NiaR structure consists of two domains: an N-terminal DNA-binding domain, and a C-terminal regulation domain containing a metal-binding site. In this paper, we report the crystal structures of apo and niacin-bound forms of NiaR from Bacillus halodurans (BhNiaR). The analysis of metal-binding and niacin-binding sites through the apo and niacin-bound structures is described. Each N- and C-terminal domain structure of BhNiaR is almost identical with NiaR from Thermotoga maritima, but the overall domain arrangement is quite different. A zinc ion is fully occupied in each subunit with well-conserved residues in the C-terminal domain. Niacin is also located at a hydrophobic pocket near the zinc ion in the C-terminal domain.
烟酸反应性阻遏物 NiaR 是对烟酰胺腺嘌呤二核苷酸 (NAD) 生物合成基因的转录阻遏物，对烟酰胺水平的增加有反应。NAD 是一种重要的分子，作为电子供体或电子受体参与各种细胞氧化还原反应。NiaR 家族在芽孢杆菌/梭菌群中广泛保守，在梭杆菌门和热脱硫杆菌门中也存在。NiaR 结构由两个结构域组成：N 端 DNA 结合结构域和包含金属结合位点的 C 端调节结构域。在本文中，我们报告了来自嗜盐芽孢杆菌 (BhNiaR) 的 NiaR 的 apo 和烟酸结合形式的晶体结构。描述了通过 apo 和烟酸结合结构对金属结合和烟酸结合位点的分析。BhNiaR 的每个 N 端和 C 端结构域结构几乎与来自海栖热袍菌的 NiaR 相同，但整体结构域排列却大不相同。锌离子在每个亚基中完全被占据，C 端结构域中的保守残基。烟酸也位于 C 端结构域中锌离子附近的疏水性口袋中。
