Gase K, Ferretti J J, Primeaux C, McShan W M
Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA.
Infect Immun. 1999 Sep;67(9):4725-31. doi: 10.1128/IAI.67.9.4725-4731.1999.
The CAMP reaction is a synergistic lysis of erythrocytes by the interaction of an extracellular protein (CAMP factor) produced by some streptococcal species with the Staphylococcus aureus sphingomyelinase C (beta-toxin). Group A streptococci (GAS [Streptococcus pyogenes]) have been long considered CAMP negative, and this reaction commonly has been used to distinguish GAS from Streptococcus agalactiae. We here provide evidence that GAS possess this gene and produce an extracellular CAMP factor capable of participating in a positive CAMP reaction. The S. pyogenes CAMP factor is specified by a 774-bp open reading frame homologous to the CAMP factor genes from S. agalactiae and Streptococcus uberis. This gene, designated cfa, was isolated on a 1,256-bp fragment and cloned in Escherichia coli. Recombinant clones of E. coli expressing cfa secreted an active CAMP factor. The deduced 28.5-kDa protein encoded by cfa consists of 257 amino acids, with a predicted 28-amino-acid signal peptide. The cfa gene is widely spread among GAS: 82 of 100 clinical GAS isolates produced a positive CAMP reaction. Of the CAMP-negative strains, 17 of the 18 GAS strains contained the cfa gene. Additionally, CAMP activity was detected in streptococci from serogroups C, M, P, R, and U. The cfa gene was cloned and actively expressed in Escherichia coli and gene fusions were made, placing the beta-galactosidase gene (lacZ) under control of the cfa promoter. These cfa promoter-lacZ fusions were introduced into S. pyogenes via a bacteriophage-derived site-specific integration vector where they showed that the cfa gene has a strong promoter that may be subject to as-yet-unidentified regulatory factors. The results presented here, along with previous reports, indicate that the CAMP factor gene is fairly widespread among streptococci, being present at least in groups A, B, C, G, M, P, R, and U.
CAMP反应是某些链球菌属产生的一种细胞外蛋白（CAMP因子）与金黄色葡萄球菌鞘磷脂酶C（β-毒素）相互作用对红细胞进行的协同溶解。A组链球菌（GAS [化脓性链球菌]）长期以来被认为CAMP反应阴性，并且该反应通常用于区分GAS与无乳链球菌。我们在此提供证据表明GAS拥有该基因并产生能够参与阳性CAMP反应的细胞外CAMP因子。化脓性链球菌CAMP因子由一个774 bp的开放阅读框指定，该开放阅读框与无乳链球菌和乳房链球菌的CAMP因子基因同源。该基因命名为cfa，在一个1256 bp的片段上分离出来并克隆到大肠杆菌中。表达cfa的大肠杆菌重组克隆分泌出一种活性CAMP因子。由cfa编码的推导28.5 kDa蛋白质由257个氨基酸组成，带有一个预测的28个氨基酸的信号肽。cfa基因在GAS中广泛分布：100株临床GAS分离株中有82株产生阳性CAMP反应。在CAMP阴性菌株中，18株GAS菌株中有17株含有cfa基因。此外，在C、M、P、R和U血清群的链球菌中检测到CAMP活性。cfa基因被克隆并在大肠杆菌中活跃表达，并构建了基因融合体，将β-半乳糖苷酶基因（lacZ）置于cfa启动子的控制之下。这些cfa启动子-lacZ融合体通过噬菌体衍生的位点特异性整合载体导入化脓性链球菌，结果表明cfa基因有一个强启动子，可能受尚未确定的调控因子影响。此处呈现的结果以及先前的报道表明，CAMP因子基因在链球菌中相当广泛地存在，至少存在于A、B、C、G、M、P、R和U群中。
