The monoclonal antibody 4B1 binds to a conformational epitope on the periplasmic side of lactose permease (LacY) of Escherichia coli and inhibits H+/lactose symport and lactose efflux under nonenergized conditions. At the same time, ligand binding and translocation reactions that do not involve net H+ translocation remain unaffected by 4B1. In this study, surface‐enhanced infrared absorption spectroscopy applied to the immobilized LacY was used to study the pH‐dependent changes in LacY and to access in situ the effect of the 4B1 antibody on the pKa of Glu325, the primary functional H+‐binding site in LacY. A small shift of the pK value from 10.5 to 9.5 was identified that can be corroborated with the inactivation of LacY upon 4B1 binding.

中文翻译：

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单克隆抗体 4B1 影响来自大肠杆菌的乳糖通透酶 (LacY) 中 Glu325 的 pKa：来自 SEIRAS 的证据

单克隆抗体 4B1 与大肠杆菌乳糖通透酶 (LacY) 周质侧的构象表位结合，并在无能量条件下抑制 H+/乳糖同向转运和乳糖流出。同时，不涉及净 H+ 易位的配体结合和易位反应不受 4B1 的影响。在这项研究中，应用到固定化 LacY 的表面增强红外吸收光谱用于研究 LacY 的 pH 依赖性变化，并原位访问 4B1 抗体对 Glu325（主要功能性 H+ 结合位点）的 pKa 的影响在花边。鉴定出 pK 值从 10.5 到 9.5 的小幅变化，这可以与 4B1 结合后 LacY 的失活得到证实。