Segarra R A, Booth M C, Morales D A, Huycke M M, Gilmore M S
Department of Microbiology and Immunology, University of Oklahoma College of Medicine, Oklahoma City 73190.
Infect Immun. 1991 Apr;59(4):1239-46. doi: 10.1128/iai.59.4.1239-1246.1991.
The gene encoding component A (cylA), the activator protein of the Enterococcus faecalis cytolysin, has been localized on pAD1, and the nucleotide sequence was determined. cylA consists of a 1,236-bp open reading frame encoding a 412-amino-acid polypeptide. A search of the National Biomedical Research Foundation data base revealed significant homology between the inferred amino acid sequence of component A and subtilisin BPN'. Component A activation of the cytolysin precursor (component L) was observed to be inhibited by the serine protease inhibitor diisopropylfluorophosphate. Mature component A exhibits a molecular weight of approximately 30,000 and an isoelectric point of 4.5. Differences between the size of the primary translation product (45,625 daltons) and the mature enzyme suggest that, as for subtilisin, component A is secreted as a proenzyme. These results provide the basis for a model of component A activation of component L and a role for component A in protecting the cytolysin-producing cell from lysis.
粪肠球菌溶血素激活蛋白A（cylA）的编码基因已定位在pAD1上，并测定了其核苷酸序列。cylA由一个1236bp的开放阅读框组成，编码一个412个氨基酸的多肽。对国家生物医学研究基金会数据库的检索显示，A组分的推断氨基酸序列与枯草杆菌蛋白酶BPN'之间存在显著同源性。观察到丝氨酸蛋白酶抑制剂二异丙基氟磷酸可抑制溶血素前体（L组分）的A组分激活。成熟的A组分分子量约为30000，等电点为4.5。初级翻译产物（45625道尔顿）与成熟酶大小的差异表明，与枯草杆菌蛋白酶一样，A组分以酶原形式分泌。这些结果为L组分的A组分激活模型以及A组分在保护产生溶血素的细胞免受裂解中的作用提供了基础。
