Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands.
Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506.
Proc Natl Acad Sci U S A. 2017 Aug 29;114(35):9439-9444. doi: 10.1073/pnas.1707032114. Epub 2017 Aug 14.
is highly adapted to its host and has evolved many strategies to resist opsonization and phagocytosis. Even after uptake by neutrophils, shows resistance to killing, which suggests the presence of phagosomal immune evasion molecules. With the aid of secretome phage display, we identified a highly conserved protein that specifically binds and inhibits human myeloperoxidase (MPO), a major player in the oxidative defense of neutrophils. We have named this protein "staphylococcal peroxidase inhibitor" (SPIN). To gain insight into inhibition of MPO by SPIN, we solved the cocrystal structure of SPIN bound to a recombinant form of human MPO at 2.4-Å resolution. This structure reveals that SPIN acts as a molecular plug that prevents HO substrate access to the MPO active site. In subsequent experiments, we observed that SPIN expression increases inside the neutrophil phagosome, where MPO is located, compared with outside the neutrophil. Moreover, bacteria with a deleted gene encoding SPIN showed decreased survival compared with WT bacteria after phagocytosis by neutrophils. Taken together, our results demonstrate that secretes a unique proteinaceous MPO inhibitor to enhance survival by interfering with MPO-mediated killing.
金黄色葡萄球菌高度适应其宿主，并进化出许多策略来抵抗调理作用和吞噬作用。即使被中性粒细胞摄取后，仍能抵抗杀伤，这表明存在吞噬体免疫逃逸分子。借助分泌噬菌体展示技术，我们鉴定出一种高度保守的蛋白，它能特异性结合并抑制人髓过氧化物酶（MPO），这是中性粒细胞氧化防御的主要参与者。我们将这种蛋白命名为“葡萄球菌过氧化物酶抑制剂”（SPIN）。为了深入了解 SPIN 对 MPO 的抑制作用，我们解析了 SPIN 与重组人 MPO 结合的共晶结构，分辨率为 2.4Å。该结构揭示 SPIN 作为一种分子塞，阻止 HO 底物进入 MPO 活性位点。在随后的实验中，我们观察到与中性粒细胞外相比，SPIN 在中性粒细胞吞噬体（MPO 所在位置）内的表达增加。此外，与野生型细菌相比，缺失编码 SPIN 的基因的细菌在被中性粒细胞吞噬后，其存活率降低。综上所述，我们的研究结果表明，金黄色葡萄球菌分泌一种独特的蛋白 MPO 抑制剂，通过干扰 MPO 介导的杀伤作用来增强其生存能力。
