PUTATIVE STRUCTURE AND FUNCTIONS OF A POLY-BETA-HYDROXYBUTYRATE CALCIUM POLYPHOSPHATE CHANNEL IN BACTERIAL PLASMA-MEMBRANES
PUTATIVE STRUCTURE AND FUNCTIONS OF A POLY-BETA-HYDROXYBUTYRATE CALCIUM POLYPHOSPHATE CHANNEL IN BACTERIAL PLASMA-MEMBRANES
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DOI：
10.1073/pnas.85.12.4176
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发表时间：
1988-06-01
影响因子：
11.1
通讯作者：
SADOFF, HL
中科院分区：
文献类型：
--
作者：
REUSCH, RN;SADOFF, HL
聚-β-从遗传感受态大肠杆菌的质膜中提取的羟基丁酸盐复合物含有摩尔比约为1：1：0.5的聚羟基丁酸盐：多磷酸盐：钙。聚羟基丁酸酯的链长估计为120-200个亚基，聚磷酸酯的链长估计为130-170个亚基。提取的复合物，当纳入脂质体，表现出脂质相变在相同的温度范围内的膜复合物在整个细胞以及相同的属性的不可逆性，责任，和敏感性螯合缓冲液。空间填充分子模型和分子能量最小化方法（Charmm）被用来开发和评估一个合理的结构的复杂。提出聚羟基丁酸酯围绕聚磷酸钙的内部框架螺旋形成外亲脂-内亲极性螺旋。钙离子通过与聚磷酸盐的磷酰氧形成离子键和与聚羟基丁酸酯的酯羰基氧形成离子偶极键来连接两种聚合物。这种对称的结构形成了一个穿过膜的通道，并可能在钙、磷酸盐和DNA的运输中发挥作用。
A poly-.beta.-hydroxybutyrate complex extracted from the plasma membranes of genetically competent Escherichia coli contained polyhyroxybutyrate:polyphosphate:calcium in molar ratios approximating 1:1:0.5. The chain length of the polyhydroxybutyrate was estimated as 120-200 subunits, and that of the polyphosphate was estimated as 130-170 subunits. The extracted complex, when incorporated into liposomes, exhibited a lipid phase transition in the same temperature range as that of the membrane complex in whole cells as well as the same properties of irreversibility, liability, and sensitivity to chelating buffers. Space-filling molecualr models and molecular energy minimization methods (Charmm) were used to develop and evaluate a plausible structure for the complex. It is proposed that the polyhydroxybutyrate forms an exolipophilic-endopolarophilic helix around an inner framework helix of calcium polyphosphate. The calcium ions link the two polymers by forming ionic bonds with phosphoryl oxygens of the polyphosphate and ion-dipole bonds with the ester carbonyl oxygens of the polyhydroxybutyrate. This symmetrical structure forms a channel through the membrane and may play a role in the transport of calcium, phosphate, and DNA.