GENETIC ANALYSIS OF STAPHYLOCOCCAL ENTEROTOXIN A

葡萄球菌肠毒素A(SEA)的生化和遗传特性 将被描述为。从核苷酸序列中获得的知识 SEA结构基因(Enta)将被用来执行位点特异性 Enta基因在可能编码氨基酸的区域的突变 参与形成SEA活性部位或受体结合的残基 域。突变的Enta基因产物将被检测呕吐活性， 有丝分裂活性和干扰素诱导。如果这些研究导致 SEA生物形成的区域识别 活性部位(S)，然后是与这些区域同源的短合成肽 将进行生物活性诱导或抑制测试。 这些研究可能导致海洋类毒素的发展，并可能 诱导干扰素或有丝分裂的新药理制剂。 金黄色葡萄球菌临床分离株中海洋产生的真实发生率 使用EntA基因探针进行检测。此外，活动站点 上面讨论的研究也可能导致开发一种 寡核苷酸探针(针对三者中存在的同源性 可识别所有肠毒素的肠毒素(SEA、SEB和SEC) 在杂交试验中产生金黄色葡萄球菌菌株。 确定SEA是否与金黄色葡萄球菌的致病性有关 同基因Enta+和Enta-金黄色葡萄球菌的相对毒力 菌株将在几个动物模型中进行测试。 内切噬菌体及相关非内切酶特性的研究 转换噬菌体将继续遗传特性和 基因组结构。这些研究可能有助于更好地理解 内切变噬菌体的自然界产生及其抗原性的机制 葡萄球菌肠毒素中产生了异质性。 Enta基因表达受到调控的可能性将通过 评估菌株背景、培养基组分和基因的影响 氯霉素-Enta-启动子融合的剂量。

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.