EXPRESSION AND PHASE VARIATION OF GONOCOCCAL OPA GENES

淋球菌 OPA 基因的表达和相变

• 批准号: 3790843
• 负责人: R J BELLAND
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3790843
• 关键词: DNA gyrase; Escherichia coli; Neisseria gonorrhoeae; bacterial DNA; bacterial genetics; bacterial proteins; cell adhesion; chimeric proteins; gene expression; genetic regulation; genetic transcription; genetic translation; host organism interaction; membrane proteins; molecular cloning; nucleic acid repetitive sequence; nucleic acid structure; recombinant DNA; structural genes; surface antigens; tissue /cell culture; transcription termination

Surface components of the human pathogen Neisseria gonorrhoeae have been shown to change dramatically during the course of gonorrheal disease in male volunteers. The Opa family of outer-membrane proteins change expression states as a result of a unique translational switching mechanism involving the insertion or deletion of discrete numbers of pentameric coding repeat elements (CR) within the segment of the gene coding for the signal-peptide of the Opa pre-protein. The direct, tandem repeat elements have the capacity to form an intramolecular triplex (H-DNA) in response to negative supercoiling torsion. The phase variation frequencies of repeated genetic elements which form H-DNA are significantly lower than elements with the same repetitive nature which are unable to form H-DNA. The enzymes responsible for generation of negative supercoiling (gyrA/B) have been cloned and are being purified to determine their effect on the transcription of opa and the relationship between transcription and H-DNA formation. A number of Opa proteins have been constitutively expressed as beta-lactamase-Opa fusions in E. coli and have been shown to segregate to the outer- membrane in a conformation resembling that seen in N. gonorrhoeae. Recombinant Opa+ bacteria mimic the interactions seen between human neutrophils and gonococcal strains expressing the analogous Opa. Recombinant strains also show an ability to adhere to certain eukaryotic cell lines in in vitro binding assays. One particular Opa fusion protein confers upon the recombinant E. coli strain the ability to adhere to and be taken up by Chang conjunctival epithelial cells. A Type III restriction modification system has been cloned from N. gonorrhoeae MS11. This system may be unique in its expression since at this time it appears that expression of the upstream methylase enzyme is translationally regulated by a series of direct tandem repeats in a manner similar to that found for the Opa system (although this has not been confirmed at this point). If found to operate as a control mechanism for expression this system will provide an interesting contrast to the Opa system with respect to the mechanisms employed for translational regulation by "illegitimate" forms of recombination.

人类病原体淋病奈瑟菌的表面成分 在淋病的过程中会发生巨大的变化 男性志愿者的疾病 外膜蛋白Opa家族 由于独特的翻译转换而改变表达状态 涉及插入或删除离散数量的 基因片段内的五聚体编码重复元件（CR） 编码Opa前蛋白的信号肽。 直接的， 串联重复元件具有形成分子内 三链体（H-DNA）对负超螺旋扭转的响应。 相位 形成H-DNA的重复遗传元件的变异频率为 明显低于具有相同重复性质的元素， 无法形成H型DNA 负责产生 负超螺旋（gyrA/B）已被克隆并正在纯化 以确定它们对OPA转录的影响， 转录和H-DNA形成之间的关系。 一些 Opa蛋白已被组成型表达为β-内酰胺酶-Opa 融合子E.大肠杆菌，并已被证明分离到外- 膜的构象类似于在N.淋病 重组Opa+细菌模拟人类之间的相互作用 表达类似Opa的嗜中性粒细胞和淋球菌菌株。 重组菌株还显示出粘附于某些真核生物的能力。 在体外结合测定中的细胞系。 一种特殊的Opa融合蛋白 赋予重组E.大肠杆菌菌株的粘附能力， 被Chang结膜上皮细胞摄取。 iii型 从N.淋病 MS 11。 这个系统可能是独特的，因为在这个时候， 上游甲基化酶的表达似乎 由一系列的直接串联重复序列调控， 类似于Opa系统的方式（尽管这没有 在这一点上得到了证实）。 如果发现作为对照 表达机制这个系统将提供一个有趣的 与Opa系统相比， 通过“非法”重组形式进行翻译调控。