Wani J H, Gilbert J V, Plaut A G, Weiser J N
Department of Pediatrics, Children's Hospital of Philadelphia, Pennsylvania, USA.
Infect Immun. 1996 Oct;64(10):3967-74. doi: 10.1128/iai.64.10.3967-3974.1996.
The pneumococcus expresses a protease that hydrolyzes human immunoglobulin A1 (IgA1). A gene for IgA1 protease was identified from a plasmid library of pneumococcal DNA because of the effect of its overexpression on the colony morphology of Streptococcus pneumoniae. The deduced 1,964-amino-acid sequence is highly homologous to that of the IgA1 protease from Streptococcus sanguis. The similarity to the S. sanguis enzyme and the presence of a putative zinc-binding site suggest that the pneumococcal enzyme is a metalloprotease. The two streptococcal sequences differ in a hydrophilic region with 10 tandem repeats of a 20-mer in S. sanguis, which is replaced by a similar but less repetitive sequence in S. pneumoniae. Antiserum reactive with the pneumococcal IgA1 protease was used to demonstrate that the majority of the protein is cell associated. The expression and function of this gene were confirmed by insertional mutagenesis. Interruption of the chromosomal gene resulted in loss of expression of an approximately 200-kDa protein and complete elimination of detectable IgA1 protease activity.
肺炎球菌表达一种可水解人免疫球蛋白A1（IgA1）的蛋白酶。由于IgA1蛋白酶过表达对肺炎链球菌菌落形态的影响，从肺炎球菌DNA的质粒文库中鉴定出了该蛋白酶的基因。推导的1964个氨基酸序列与血链球菌的IgA1蛋白酶高度同源。与血链球菌酶的相似性以及假定的锌结合位点的存在表明，肺炎球菌酶是一种金属蛋白酶。两种链球菌序列在血链球菌中一个具有20聚体10个串联重复的亲水区不同，在肺炎链球菌中该区域被一个相似但重复较少的序列所取代。用与肺炎球菌IgA1蛋白酶反应的抗血清证明，大多数该蛋白与细胞相关。通过插入诱变证实了该基因的表达和功能。染色体基因的中断导致约200 kDa蛋白的表达丧失以及可检测到的IgA1蛋白酶活性完全消除。
