Kellogg T A, Lazaron V, Wasiluk K R, Dunn D L
Department of Surgery, University of Minnesota, Minneapolis 55455, USA.
Shock. 2001 Feb;15(2):124-9. doi: 10.1097/00024382-200115020-00008.
The deep core/lipid A (DCLA) region of gram-negative bacterial lipopolysaccharide (LPS) is common to most gram-negative pathogens and contains anionic phosphoryl groups plus numerous acyl chains as part of the toxic lipid A moiety. Several disparate agents that antagonize the effects of LPS exhibit extensive physicochemical similarities (hydrophobicity, cationic charge) within their binding domains. It is presumed that binding to the DCLA region by each of these antagonists-cross-reactive anti-LPS monoclonal antibodies (mAbs), polymyxin B (PmB), plus bactericidal permeability-increasing protein (BPI) and Limulus anti-LPS factor (LALF)-may be related to these properties. Therefore, we hypothesized that in addition to secondary and tertiary protein conformation, electrostatic interactions involving the negatively charged phosphoryl groups, hydrophobic interactions involving the acyl chains of lipid A, or both might be important factors that promote LPS antagonism. Binding of PmB, BPI, LALF, or anti-DCLA mAb 1B6 to Salmonella minnesota monophosphoryl lipid A (MPLA), diphosphoryl lipid A (DPLA), and Salmonella minnesota Re (which possess a common structural moiety, but vary considerably in structure and charge) was examined. Highly phosphorylated DNA and bovine serum albumin served as unrelated structural controls. BPI bound MPLA, which is hydrophobic and minimally charged, while mAb 1B6 bound anionic DNA; neither PmB nor LALF were reactive with MPLA or DNA. We surmised that hydrophobic interactions play a role in BPI binding to LPS, and although electrostatic interactions appear to be important for binding of mAb 1B6 to DCLA, they may not contribute to as great an extent for PmB, BPI, or LALF. Thus our data support the contention that the contribution of these specific physicochemical factors varies among endotoxin antagonists.
革兰氏阴性菌脂多糖（LPS）的深层核心/脂质A（DCLA）区域是大多数革兰氏阴性病原体所共有的，并且含有阴离子磷酸基团以及众多酰基链，这些是有毒脂质A部分的组成部分。几种不同的拮抗LPS作用的试剂在其结合域内表现出广泛的物理化学相似性（疏水性、阳离子电荷）。据推测，这些拮抗剂——交叉反应性抗LPS单克隆抗体（mAb）、多粘菌素B（PmB）、杀菌通透性增加蛋白（BPI）和鲎抗LPS因子（LALF）——与DCLA区域的结合可能与这些特性有关。因此，我们推测，除了二级和三级蛋白质构象外，涉及带负电荷的磷酸基团的静电相互作用、涉及脂质A酰基链的疏水相互作用，或两者都可能是促进LPS拮抗作用的重要因素。研究了PmB、BPI、LALF或抗DCLA mAb 1B6与明尼苏达沙门氏菌单磷酸脂质A（MPLA）、二磷酸脂质A（DPLA）和明尼苏达沙门氏菌Re（它们具有共同的结构部分，但在结构和电荷上有很大差异）的结合情况。高度磷酸化的DNA和牛血清白蛋白作为无关的结构对照。BPI结合了疏水性且电荷最少的MPLA，而mAb 1B6结合了阴离子DNA；PmB和LALF都不与MPLA或DNA反应。我们推测疏水相互作用在BPI与LPS的结合中起作用，尽管静电相互作用似乎对mAb 1B6与DCLA的结合很重要，但它们对PmB、BPI或LALF的贡献可能没那么大。因此，我们的数据支持这样的观点，即这些特定物理化学因素的贡献在内毒素拮抗剂之间存在差异。
