Structural Biology of Phagocyte oxidation

吞噬细胞NADPH氧化酶是一种微生物感染的防御系统，它由膜结合的黄色素细胞色素Cyt(gp91；lt；Phox&gt；和p22^&lt；Phox&gt；)和胞浆因子p67^&lt；Phox&gt；，p47^&lt；Phox&gt；，p40^&lt；Phox&gt；和小GTP酶RAC组成。在微生物入侵时，胞质因子被转移到细胞膜上，与细胞色素b_(558)结合，激活细胞色素b_(558)的氧化还原核心，产生杀菌氧化剂的前体O_2-。NADPH氧化酶的激活是通过p47^&lt；Phox&gt；串联SH3结构域的构象变化来严格调控的。最近，以自抑制形式(Groemping et al.，Cell，2003，Yuzawa et al.，gene Cells，2004，J Biol Chem.，2004)和激活形式(Groemping等人，Cell，2003)的串联SH3结构域的晶体结构被确定。有趣的是，串联的SH3结构域在晶态下形成了相互缠绕的二聚体，但分裂的一半被认为是生理相关的。在这里，我们用核磁共振技术研究了串联SH3结构域的掩蔽态和非掩蔽态的三维结构。此外，我们还通过小角X射线散射阐明了串联SH3结构域从掩蔽态到非掩蔽态的整体构象变化。根据目前的结构数据，我们讨论了吞噬细胞NADPH氧化酶的激活机制。

The phagocyte NADPH oxidase, a defense system for microbial infection comprises membrane bound flavocytochrome cyt b_<558> (gp91^<phox> and p22^<phox>) and cytosolic factors including p67^<phox>, p47^<phox>, p40^<phox> and small GTPase Rac. Upon microbial invasion, the cytosolic factors are translocated to the membrane to bind to cyt b_<558>, which activates a redox-core of cyt b_<558> and generates O_2-, a precursor of microbicidal oxidants. The activation of the NADPH oxidase is tightly regulated through conformation change of the tandem SH3 domain of p47^<phox>.Recently, the crystal structure of the tandem SH3 domains in the autoinhibited form (Groemping et al., Cell,2003, Yuzawa et al., Genes Cells,2004, J Biol Chem.,2004) and the activated form (Groemping et al., Cell,2003) were determined. Interestingly, the tandem SH3 domains formed an intertwisted dimer in the crystal state but the splitted half was considered to be physiologically relevent. Here, we report the three dimensional structures of the masked and unmasked states of the tandem SH3 domains by NMR. Furthermore, we elucidated the global conformation change of the tandem SH3 domains from the masked to unmasked states by small angle X-ray scattering. Based on the present structural data, we discussed the activation mechanism of the phagocyte NADPH oxidase.