Centre de Biophysique Moléculaire, UPR 4301 CNRS, Rue Charles Sadron, Orléans 2 45071, France.
EMBO Rep. 2011 Apr;12(4):327-33. doi: 10.1038/embor.2011.19. Epub 2011 Mar 4.
The peptidoglycan (PGN)-recognition protein LF (PGRP-LF) is a specific negative regulator of the immune deficiency (Imd) pathway in Drosophila. We determine the crystal structure of the two PGRP domains constituting the ectodomain of PGRP-LF at 1.72 and 1.94 Å resolution. The structures show that the LFz and LFw domains do not have a PGN-docking groove that is found in other PGRP domains, and they cannot directly interact with PGN, as confirmed by biochemical-binding assays. By using surface plasmon resonance analysis, we show that the PGRP-LF ectodomain interacts with the PGRP-LCx ectodomain in the absence and presence of tracheal cytotoxin. Our results suggest a mechanism for downregulation of the Imd pathway on the basis of the competition between PRGP-LCa and PGRP-LF to bind to PGRP-LCx.
肽聚糖(PGN)识别蛋白 LF(PGRP-LF)是果蝇免疫缺陷(Imd)途径的特异性负调节剂。我们确定了由 PGRP-LF 的胞外结构域组成的两个 PGRP 结构域的晶体结构,分辨率分别为 1.72 和 1.94 Å。这些结构表明,LFz 和 LFw 结构域没有其他 PGRP 结构域中发现的 PGN 结合槽,并且它们不能直接与 PGN 相互作用,这一点通过生化结合测定得到了证实。通过表面等离子体共振分析,我们表明在存在和不存在气管细胞毒素的情况下,PGRP-LF 胞外结构域与 PGRP-LCx 胞外结构域相互作用。我们的结果表明,基于 PRGP-LCa 和 PGRP-LF 与 PGRP-LCx 结合的竞争,存在一种下调 Imd 途径的机制。