Yokohama City University, Suehiro 1-7-29, Tsurumi, Yokohama 230-0045, Japan.
J Mol Biol. 2010 Feb 26;396(3):634-45. doi: 10.1016/j.jmb.2009.11.055. Epub 2009 Dec 1.
We have determined high-resolution apo crystal structures of two low molecular weight penicillin-binding proteins (PBPs), PBP4 and PBP5, from Haemophilus influenzae, one of the most frequently found pathogens in the upper respiratory tract of children. Novel beta-lactams with notable antimicrobial activity have been designed, and crystal structures of PBP4 complexed with ampicillin and two of the novel molecules have also been determined. Comparing the apo form with those of the complexes, we find that the drugs disturb the PBP4 structure and weaken X-ray diffraction, to very different extents. PBP4 has recently been shown to act as a sensor of the presence of penicillins in Pseudomonas aeruginosa, and our models offer a clue to the structural basis for this effect. Covalently attached penicillins press against a phenylalanine residue near the active site and disturb the deacylation step. The ready inhibition of PBP4 by beta-lactams compared to PBP5 also appears to be related to the weaker interactions holding key residues in a catalytically competent position.
我们已经确定了两种来自流感嗜血杆菌（儿童上呼吸道最常见的病原体之一）的低分子量青霉素结合蛋白（PBPs），即 PBP4 和 PBP5 的高分辨率无蛋白晶体结构。已经设计出具有显著抗菌活性的新型β-内酰胺类药物，并且还确定了 PBP4 与氨苄西林和两种新型分子复合物的晶体结构。将无蛋白形式与复合物的形式进行比较，我们发现这些药物以不同的程度干扰 PBP4 结构并削弱 X 射线衍射。最近已经表明，PBP4 作为铜绿假单胞菌中青霉素存在的传感器，我们的模型为这种作用的结构基础提供了线索。共价连接的青霉素紧贴在靠近活性位点的苯丙氨酸残基上，并干扰去酰化步骤。与 PBP5 相比，β-内酰胺类药物对 PBP4 的快速抑制作用似乎也与保持关键残基处于催化能力位置的较弱相互作用有关。
