Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
PLoS One. 2009 Nov 30;4(11):e8017. doi: 10.1371/journal.pone.0008017.
The Dps (DNA-binding protein from starved cells) proteins from Mycobacterium smegmatis MsDps1 and MsDps2 are both DNA-binding proteins with some differences. While MsDps1 has two oligomeric states, with one of them responsible for DNA binding, MsDps2 has only one DNA-binding oligomeric state. Both the proteins however, show iron-binding activity. The MsDps1 protein has been shown previously to be induced under conditions of starvation and osmotic stress and is regulated by the extra cellular sigma factors sigma(H) and sigma(F). We show here, that the second Dps homologue in M. smegmatis, namely MsDps2, is purified in a DNA-bound form and exhibits nucleoid-like structures under the atomic force microscope. It appears that the N-terminal sequence of Dps2 plays a role in nucleoid formation. MsDps2, unlike MsDps1, does not show elevated expression in nutritionally starved or stationary phase conditions; rather its promoter is recognized by RNA polymerase containing sigma(A) or sigma(B), under in vitro conditions. We propose that due to the nucleoid-condensing ability, the expression of MsDps2 is tightly regulated inside the cells.
来自饥饿细胞的 Dps（DNA 结合蛋白）蛋白，来自分枝杆菌的 MsDps1 和 MsDps2 都是具有一些差异的 DNA 结合蛋白。虽然 MsDps1 有两种寡聚状态，其中一种负责 DNA 结合，但 MsDps2 只有一种 DNA 结合寡聚状态。然而，这两种蛋白质都具有铁结合活性。以前已经表明，MsDps1 蛋白在饥饿和渗透胁迫条件下被诱导，并受细胞外 sigma 因子 sigma(H)和 sigma(F)的调节。我们在这里表明，分枝杆菌中的第二个 Dps 同源物，即 MsDps2，以 DNA 结合形式被纯化，并在原子力显微镜下显示出类核样结构。似乎 Dps2 的 N 端序列在核形成中起作用。与 MsDps1 不同，MsDps2 不会在营养饥饿或静止期条件下表现出升高的表达；相反，其启动子在体外条件下被含有 sigma(A)或 sigma(B)的 RNA 聚合酶识别。我们提出，由于类核浓缩能力，MsDps2 的表达在细胞内受到严格调控。
