Treponema denticola is a proteolytic‐anaerobic spirochete whose abundance in the subgingival crevice correlates with periodontal disease severity. Treponema denticola evades serum‐mediated killing through the binding of factor H (FH), a negative regulator of the complement system. The T. denticolaFH receptor has been identified as FhbB, an 11.4kDa immunodominant lipoprotein. Three distinct subfamilies of FhbB proteins have been delineated and designated as FhbB1, FhbB2 and FhbB3. In this study we demonstrate that all FhbB variants bind human plasminogen (Plg). Competitive binding analyses revealed that FH and Plg do not compete for binding. Binding studies with FhbB1₃₅₄₀₅ site‐directed amino acid substitution mutants demonstrated that the interaction domains for FH and Plg on FhbB are separable. Inhibition of Plg‐FhbB binding by ε‐aminocaproic acid (a lysine analog) indicates that binding is mediated by electrostatic interactions that presumably occur with Lys binding sites contained within Plg “Kringle” domains 1, 2, 4 or 5. Similar to that demonstrated for FH, Plg can also serve as a substrate for the T. denticola protease, dentilisin. The in vivo consequences of dentilisin‐mediated cleavage of Plg remained to be determined. The data presented demonstrate that FhbB is a multi‐functional protein that may contribute to virulence through several mechanisms including immune evasion, manipulation of the host immune response, adherence or tissue invasion.

中文翻译：

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血浆纤溶酶原结合和降解反应：鉴定FhbB蛋白上的纤溶酶原结合界面。

密螺旋体是一种蛋白水解厌氧螺旋体，其龈下缝隙中的丰度与牙周疾病的严重程度相关。密螺旋体通过结合补体系统的负调节因子H（FH）逃避血清介导的杀伤。该T.齿垢FH受体已被确定为FhbB，一个11.4kDa免疫脂蛋白。已经描述了FhbB蛋白的三个不同的亚家族，并命名为FhbB1，FhbB2和FhbB3。在这项研究中，我们证明了所有FhbB变体都结合人纤溶酶原（Plg）。竞争性结合分析显示FH和Plg不竞争结合。与FhbB1 _35405的结合研究定点氨基酸取代突变体表明FhbB上FH和Plg的相互作用域是可分离的。ε-氨基己酸（赖氨酸类似物）对Plg-FhbB结合的抑制表明结合是由静电相互作用介导的，该相互作用可能与Plg“ Kringle”结构域1、2、4或5中包含的Lys结合位点发生。对于FH，Plg还可作为T. denticola蛋白酶牙本质素的底物。牙本质素介导的Plg裂解的体内结果仍有待确定。呈现的数据表明FhbB是一种多功能蛋白，可能通过多种机制（包括逃避免疫，操纵宿主免疫应答，粘附或组织侵袭）促进毒力。