New York State Department of Health, Stony Brook University, Stony Brook, NY 11794-5120, USA.
Mol Microbiol. 2013 May;88(3):619-33. doi: 10.1111/mmi.12213. Epub 2013 Apr 9.
Borrelia burgdorferi, the spirochaetal agent of Lyme disease, codes for a single HtrA protein, HtrABb (BB0104) that is homologous to DegP of Escherichia coli (41% amino acid identity). HtrABb shows physical and biochemical similarities to DegP in that it has the trimer as its fundamental unit and can degrade casein via its catalytic serine. Recombinant HtrABb exhibits proteolytic activity in vitro, while a mutant (HtrABbS198A) does not. However, HtrABb and DegP have some important differences as well. Native HtrABb occurs in both membrane-bound and soluble forms. Despite its homology to DegP, HtrABb could not complement an E. coli DegP deletion mutant. Late stage Lyme disease patients, as well as infected mice and rabbits developed a robust antibody response to HtrABb, indicating that it is a B-cell antigen. In co-immunoprecipitation studies, a number of potential binding partners for HtrABb were identified, as well as two specific proteolytic substrates, basic membrane protein D (BmpD/BB0385) and chemotaxis signal transduction phosphatase CheX (BB0671). HtrABb may function in regulating outer membrane lipoproteins and in modulating the chemotactic response of B. burgdorferi.
伯氏疏螺旋体，莱姆病的螺旋体病原体，编码一种单一的 HtrA 蛋白，HtrABb（BB0104），与大肠杆菌的 DegP 同源（41%的氨基酸同一性）。HtrABb 在物理和生化性质上与 DegP 相似，因为它的基本单元是三聚体，并且可以通过催化丝氨酸降解酪蛋白。重组 HtrABb 在体外表现出蛋白水解活性，而突变体（HtrABbS198A）则没有。然而，HtrABb 和 DegP 也有一些重要的区别。天然 HtrABb 以膜结合和可溶性两种形式存在。尽管与 DegP 同源，但 HtrABb 不能补充大肠杆菌 DegP 缺失突变体。晚期莱姆病患者以及感染的小鼠和兔子对 HtrABb 产生了强烈的抗体反应，表明它是一种 B 细胞抗原。在共免疫沉淀研究中，鉴定出 HtrABb 的许多潜在结合伴侣，以及两种特定的蛋白水解底物，碱性膜蛋白 D（BmpD/BB0385）和趋化性信号转导磷酸酶 CheX（BB0671）。HtrABb 可能在调节外膜脂蛋白和调节伯氏疏螺旋体的趋化反应中发挥作用。
