Studies on Enzyme Mechanism and Antibiotic Resistance Strategies

耐药菌株的出现对人类健康构成了日益严重的问题。细菌的快速变异能力和对临床使用的抗生素的防御机制意味着，我们很快就会用完对抗细菌感染的有效药物。这项提案描述了三个项目，它们将帮助我们了解并可能控制细菌防御机制，使它们能够在人类宿主中生存。第一个项目涉及一种酶，它能产生一种名为葡萄黄素的化合物，帮助致病菌金黄色葡萄球菌在人体内存活。我们的提案描述了将揭示这种酶如何构建这种分子的研究。这些知识可以用来制备分子，阻止这种酶发挥作用，从而剥夺细菌的防御机制。然后，这些分子可以被用作抗生素。第二和第三个项目围绕细菌用来逃避临床使用的抗生素的耐药性机制。在第二个项目中，我们的目标是一种名为AMPG的蛋白质，它在对青霉素等β-内酰胺类抗生素的耐药性中发挥关键作用。当AMPG起作用时，它有助于“感觉”抗生素的存在，并导致细菌产生一种名为β-内酰胺酶的酶，然后破坏抗生素。这使得抗生素无效，并允许感染传播。我们计划研究AMPG的运作方式，并发现哪些分子最能有效地使其产生β-内酰胺酶。干扰AMPG功能可以使β-内酰胺类抗生素再次有效发挥作用。在第三个项目中，我们研究了一种名为ARND的酶，它与某些致病菌株对抗生素多肽(如多粘菌素)的耐药性有关。这种酶有助于在细菌表面覆盖一层分子，防止抗生素与细菌结合并杀死细菌。我们计划第一次展示ARND的活性，并研究它是如何产生“包衣”化合物的。这最终可能导致ARND抑制剂的产生，从而阻止其发挥作用，从而揭开细菌的面纱，使它们对抗生素敏感。

The emergence of resistant strains of bacteria presents an ever-increasing problem to human health. The ability of bacteria to rapidly mutate and develop defense mechanisms against clinically used antibiotics means that we will soon run out of effective drugs to combat bacterial infections. This proposal describes three projects that will help us to understand and possibly control the bacterial defense mechanisms that allow them to survive in a human host. The first project involves an enzyme that produces a compound called staphyloxanthin that helps the pathogenic bacteria Staphylococcus aureus survive in the human body. Our proposal describes studies that will uncover how the enzyme constructs this molecule. Such knowledge can be used to prepare molecules that will prevent the enzyme from doing its job, and thereby depriving the bacteria of their defense mechanism. Such molecules could then be used as antibiotics. The second and third projects revolve around resistance mechanisms that bacteria use to evade clinically used antibiotics. In the second project we are targeting a protein called AmpG that plays a key role in resistance to the beta-lactam antibiotics, such as penicillin. When AmpG is functional it helps to "sense" the presence of the antibiotic and leads the bacteria to produce an enzyme called a beta-lactamase that then destroys the antibiotic. This renders the antibiotic ineffective and allows the infection to spread. We plan to study the way AmpG operates and discover which molecules are most effective at getting it to signal beta-lactamase production. Interfering with AmpG function could allow the beta-lactam antibiotics to function effectively once again. In the third project, we study an enzyme called ArnD that is involved in the resistance of certain pathogenic strains of bacteria against antibiotic peptides such as polymyxin. This enzyme helps to coat the surface of the bacteria with molecules that prevent the antibiotic from binding and killing the bacteria. We plan to demonstrate the activity of ArnD for the first time and to study how it generates the "coating" compounds. This may ultimately lead to the production of inhibitors of ArnD that could prevent it from functioning, thereby unmasking the bacteria and leaving them susceptible to antibiotics.