Equilibrium binding behavior of magnesium to wall teichoic acid.
Equilibrium binding behavior of magnesium to wall teichoic acid.
复制标题
镁与壁磷壁酸的平衡结合行为。
DOI：
10.1016/j.bbamem.2015.05.003
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Rice,CharlesV
中科院分区：
文献类型：
--
作者：
Thomas3rd,KiethJ;Rice,CharlesV
肽聚糖和磷壁酸是革兰氏阳性菌的主要细胞壁成分，可获取和隔离生化过程所需的金属离子。肽聚糖内和沿着磷壁酸磷酸二酯聚合物的阴离子结合位点有助于金属向细胞质膜的递送。与金属的相互作用是吸引力和离子扩散到膜的需要之间的微妙平衡。同样，来自细胞外液的金属螯合最初必须具有很强的结合能量，该结合能量在细胞壁内减弱以实现离子释放。我们采用原子吸收和平衡透析来测量壁磷壁酸和 Mg2+ 的金属结合能力和金属结合亲和力。数据显示，Mg2 + 以 1:2 Mg2 + 与磷酸盐的比例与 WTA 结合，结合容量为 1.27 μmol/mg。还发现，由于静电效应减弱，在低金属浓度下，Mg2 + 与 WTA 的亲和力为 41 × 103M−1，在较高 Mg2+ 浓度下，Mg2+ 与 WTA 的亲和力为 1.3 × 103M−1。这些值低于描述 Mg2 + 与肽聚糖相互作用的值。然而，WTA的结合能力比肽聚糖大4倍。外部WTA最初以正协同性结合金属，但金属结合转变为负协同性，而内部WTA仅以负协同性结合金属。这项工作的相关性是描述金属结合行为随环境的变化。当金属稀少时，螯合作用很强以确保生存，但当必需矿物质丰富时，螯合作用就会减弱。
Peptidoglycan and teichoic acids are the major cell wall components of Gram-positive bacteria that obtain and sequester metal ions required for biochemical processes. The delivery of metals to the cytoplasmic membrane is aided by anionic binding sites within the peptidoglycan and along the phosphodiester polymer of teichoic acid. The interaction with metals is a delicate balance between the need for attraction and ion diffusion to the membrane. Likewise, metal chelation from the extracellular fluid must initially have strong binding energetics that weaken within the cell wall to enable ion release. We employed atomic absorption and equilibrium dialysis to measure the metal binding capacity and metal binding affinity of wall teichoic acid and Mg2 +. Data show that Mg2 +binds to WTA with a 1:2 Mg2 +to phosphate ratio with a binding capacity of 1.27 μmol/mg. The affinity of Mg2 +to WTA was also found to be 41 × 103M− 1at low metal concentrations and 1.3 × 103M− 1at higher Mg2 +concentrations due to weakening electrostatic effects. These values are lower than the values describing Mg2 +interactions with peptidoglycan. However, the binding capacity of WTA is 4 times larger than peptidoglycan. External WTA initially binds metals with positive cooperativity, but metal binding switches to negative cooperativity, whereas interior WTA binds metals with only negative cooperativity. The relevance of this work is to describe changes in metal binding behavior depending on environment. When metals are sparse, chelation is strong to ensure survival yet the binding weakens when essential minerals are abundant.