GENETIC ANALYSIS OF STAPHYLOCOCCAL ENTEROTOXIN A

葡萄球菌肠毒素A（SEA）的生化和遗传特性 将被定性。 从核苷酸序列中获得的知识 SEA结构基因（entA）将用于进行位点特异性 在可能编码氨基酸的区域中诱变entA基因， 参与形成SEA活性位点或受体结合的残基 域 将测定突变的entA基因产物的催吐活性， 促有丝分裂活性和干扰素诱导。 如果这些研究导致 识别参与SEA生物学形成的区域 活性位点，然后是与这些区域同源的短合成肽 将检测生物活性的诱导或抑制。 这些研究可能导致SEA类毒素的发展， 用于诱导干扰素或有丝分裂的新药理学试剂。 在临床分离的S.金黄色将 使用entA基因探针测定。 此外，活动现场 上面讨论的研究也可能导致一种 寡核苷酸探针（针对存在于三个寡核苷酸序列中的同源性， 肠毒素SEA、SEB和SEC）， 在杂交测定中产生金黄色葡萄球菌菌株。 为了确定SEA是否参与了S.金黄色 菌株，EntA+和EntA-S的相对毒力。金黄色 将在几种动物模型中测试菌株。 entA转化酶和相关非entA酶的表征 将继续对遗传特性进行转换， 基因组结构 这些研究可能会导致更好地了解如何 entA转换酶在自然界中产生，抗原性 在葡萄球菌肠毒素中产生异质性。 将通过以下方法检查entA基因表达受调节的可能性： 评估菌株背景、培养基组成和基因的影响 剂量对氯霉素-entA-启动子融合的影响。

The biochemical and genetic properties of staphylcoccal enterotoxin A (SEA) will be characterized. Knowledge gained from the nucleotide sequence of the SEA structural gene (entA) will be used to perform site-specific mutagenesis of the entA gene in regions likely to encode amino acid residues involved in formation of the SEA active site or receptor binding domain. The mutant entA gene products will be assayed for emetic activity, mitogenic activity and interferon induction. If these studies lead to the identification of regions involved in the formation of SEA's biological active site(s), then short synthetic peptides homologous to these regions will be tested for the induction or inhibition of biological activities. These studies could lead to the development of SEA toxoids, and possibly new pharmacological agents for the induction of interferon or mitogenesis. The true incidence of SEA production in clinical isolates of S. aureus will be determined using an entA gene probe. In addition, the active site studies discussed above may also result in the development of an oligonuleotide probe (directed at homologies present in the three enterotoxins SEA, SEB and SEC) that might identify all enterotoxin producing Staphylococcus aureus strains in a hybridization assay. To determine if SEA can contribute to the pathogenicity of S. aureus strains, the relative virulence of isogenic EntA+ and EntA- S. aureus strains will be tested in several animal models. Characterization of the entA-converting phages and related non-entA converting phages will continue with respect to genetic properties and genome structure. These studies may lead to a better understanding of how entA-converting phages arise in nature and the mechanism by which antigenic heterogeneity is generated in the staphylococcal enterotoxins. The possibility that entA gene expression is regulated will be examined by assessing the effects of strain background, media composition, and gene dosage on a chloramphenicol-entA-promoter fusion.