Significance of four methionine sulfoxide reductases in Staphylococcus aureus

描述(申请人提供)：PI实验室的长期目标是发展对金黄色葡萄球菌致病的遗传基础的了解，并找到克服其对抗生素的耐药性的方法。本研究的目的是确定蛋氨酸亚麻酸还原酶(MSR)在该生物体中的确切生理作用。蛋白质结合的蛋氨酸残基的氧化会导致生物活性丧失。MSR酶可减少氧化应激下蛋氨酸亚砜(MetO)的生成，恢复蛋白质功能。用细胞壁活性抗生素处理的金黄色葡萄球菌细胞产生的MSR酶数量增加。金黄色葡萄球菌有三个基因(msrA1、msrA2和msrA3)和一个编码蛋白(MsrB)，这三个基因编码与胃动素的S异构体还原有关的蛋白。金黄色葡萄球菌为什么具有多个功能明显重叠或冗余的蛋白质，以及它们在生理和毒力中的作用尚不清楚。假设编码这些MSR蛋白的基因在不同的环境条件下有不同的表达，它们的产物保护金黄色葡萄球菌免受胁迫条件的影响。为了验证这一假设，已经构建了各种报告菌株和MSR突变菌株。在适当的生长条件下，金黄色葡萄球菌菌株将被用来确定负责产生四种MSR蛋白的基因的表达模式。为本研究构建的三个独特的msr突变体包括一个msrB突变体(缺乏还原R-meto的能力)、一个三重msr突变体(msrA1、msrA2、msrA3；缺乏还原S-meto的能力)和一个四重msr突变体(msrA1、msrA2、msrA3、msrB；缺乏还原R-或S-meto的能力)。这些突变体将通过进行适当的体外和体内实验来确定MSR蛋白在葡萄球菌生理和毒力中的确切作用。这项研究将为杜鲁门州立大学本科生和ATU研究生提供广泛的研究培训。这项研究的完成将使人们更好地了解四种MSR蛋白在金黄色葡萄球菌中的重要性，并为控制这种病原体引起的感染开辟新的途径。 公共卫生相关性：金黄色葡萄球菌是一种重要的人类病原体。抗生素处理的金黄色葡萄球菌细胞产生大量的蛋氨酸亚砜还原酶(MSR)蛋白质。确定四种MSR蛋白的确切生理功能将有助于了解一般的应激耐受性，特别是金黄色葡萄球菌的抗生素耐药性，并将为控制葡萄球菌感染提供新的治疗策略。

DESCRIPTION (provided by applicant): The long-term goal of the PI's laboratory is to develop an understanding of the genetic basis of Staphylococcus aureus pathogenesis and find ways to overcome its ability to express resistance to antibiotics. The purpose of this study is to determine precise physiological roles of methionine sulfoxide reductase (Msr) enzymes in this organism. Oxidation of protein bound methionine residues leads to loss of biological activity. Msr enzymes reduce methionine sulfoxide (MetO) generated under oxidative stress and restore protein function. S. aureus cells treated with cell wall-active antibiotics produce elevated amounts of Msr enzymes. S. aureus possesses three genes that encode proteins involved in the reduction of the S-epimer of MetO (msrA1, msrA2, and msrA3) and a gene, msrB, that encodes a protein involved in the reduction of the R-epimer of MetO. Why S. aureus possesses multiple proteins with apparently overlapping or redundant functions, and their roles in physiology and virulence are not clear. It is hypothesized that the genes encoding these Msr proteins are expressed differentially under different environmental conditions and that their products protect S. aureus from stress conditions. To test this hypothesis, various reporter and msr mutant strains have been constructed. The reporter S. aureus strains will be used to determine, under appropriate growth conditions, the expression patterns of the genes that are responsible for producing the four Msr proteins. The three unique msr mutants constructed for this study include an msrB mutant (lacks ability to reduce R-MetO); a triple msr mutant (msrA1, msrA2, msrA3; lacks ability to reduce S-MetO); and a quadruple msr mutant (msrA1, msrA2, msrA3, msrB; lacks ability to reduce either R- or S-MetO). These mutants will be used to determine the precise roles of Msr proteins in staphylococcal physiology and virulence by conducting appropriate in vitro and in vivo experiments. This study will provide extensive research training for Truman State University undergraduate and ATSU graduate students. Completion of the study will provide a better understanding of the significance of four Msr proteins in S. aureus and open avenues to control infections caused by this pathogen. PUBLIC HEALTH RELEVANCE: Staphylococcus aureus is a significant human pathogen. Antibiotic treated S. aureus cells produce elevated amounts of methionine sulfoxide reductase (Msr) proteins. Determination of the precise physiological roles of the four Msr proteins will help understand stress tolerance in general and antibiotic resistance in particular in S. aureus, and should suggest new therapeutic strategies for the control of staphylococcal infections.