SpyA, a novel S. pyogenes ADP-ribosyltransferase

描述（由申请方提供）：化脓性链球菌是一种普遍存在的多功能人类病原体。由该微生物引起的感染范围从相对轻微和常见的咽炎和脓疱到急性和危及生命的坏死性筋膜炎和中毒性休克。链球菌疾病的广泛范围部分是由于产生许多不同的细胞外毒素和酶。这项资助的重点是最近描述的一种链球菌毒素，我们称之为间谍A。化脓菌ADP-核糖基化毒素。SpyA将NAD的ADP-核糖部分转移到细胞骨架蛋白波形蛋白、肌动蛋白和原肌球蛋白上。虽然肌动蛋白被其他ADP-核糖基转移酶修饰，但波形蛋白和原肌球蛋白不是常见的靶点。肌动蛋白和波形蛋白丝是需要运动的细胞功能所必需的，例如伤口愈合和吞噬作用期间的细胞迁移。SpyA是外毒素C3家族的成员，并且与该家族的每个成员相似，不具有明显的受体结合结构域或二元毒素所发现的相关结合结构域。我们提出SpyA通过胆固醇依赖性溶细胞素SLO产生的孔进入真核细胞。这项资助的目的是（1）确定SpyA在链球菌感染中的作用，（2）表征其新的进入机制和（3）表征这种毒素的结构和生化活性。

DESCRIPTION (provided by applicant): Streptococcus pyogenes is a ubiquitous and versatile human pathogen. Infections due to this organism range from the relatively mild and common pharyngitis and impetigo to the acute and life-threatening necrotizing fasciitis and toxic shock. The wide spectrum of streptococcal disease results in part from the production of the many and varied extracellular toxins and enzymes. The focus of this grant is a recently described streptococcal toxin we term Spy A, for S. pyogenes ADP-ribosylating toxin. SpyA transfers the ADP-ribose portion of NAD onto the cytoskeletal proteins vimentin, actin, and tropomyosin. While actin is modified by other ADP-ribosyltransferases, vimentin and tropomyosin are not common targets. Actin and vimentin filaments are needed for cellular functions requiring motility, such as cell migration during wound healing and phagocytosis. SpyA is a member of the C3 family of exotoxins, and similar to each member of this family, does not have an obvious receptor-binding domain, or associated binding domain as found with binary toxins. We proposed that SpyA gains entrance into the eukaryotic cell using a pore produced by the cholesterol dependent cytolysin SLO. The goals of this grant are (1) to determine the role of SpyA in streptococcal infections, (2) to characterize its novel entry mechanism and (3) to characterize the structure and biochemical activity of this toxin.