Principles of Protein Mimicry of DNA

描述（由申请人提供）：本修订后的新申请描述了对最近发现的五肽重复蛋白（PRP）蛋白家族成员的“DNA拟态”的全面生化和生物物理研究。结核分枝杆菌MfpA PRP的原子分辨结构揭示了一个新的蛋白折叠；MfpA的右手2螺旋线圈产生了一个细长的结构，这是一个非凡的模仿DNA的大小，形状和静电表面。DNA模仿对MfpA的生物学作用很重要，这表明它能够通过结合DNA回转酶从而抑制其功能而赋予对氟喹诺酮类药物的抗性。我们将验证MfpA对DNA物理特性的模仿是其赋予耐药性能力的核心这一假设。我们的长期目标是了解MfpA和其他PRP介导抗生素耐药性的分子机制，并可能调节DNA的酶促加工。MfpA将被开发为一个模型系统，用于探索这种新发现和广泛分布的一类蛋白质的DNA模仿。氟喹诺酮类药物因其对革兰氏阳性、革兰氏阴性和分枝杆菌的疗效而成为极为重要的抗生素。氟喹诺酮类药物以独特的作用机制作用于DNA旋切酶。值得注意的是，它们没有毒性，治疗指数是目前所有处方抗生素中最高的。由于质粒编码蛋白的表达，氟喹诺酮类药物耐药的传播形式迅速出现和蔓延，威胁到这些抗生素的临床应用。拟议的研究旨在了解肽重复蛋白MfpA和Qnr的物理性质如何产生对氟喹诺酮类药物的抗性。这一认识将为氟喹诺酮类药物的补充治疗提供新的靶点，以对抗prp介导的耐药性。相反，了解这些蛋白质的功能机制可能会使PRP折叠成为开发新型蛋白质或肽疗法的平台。

DESCRIPTION (provided by applicant): This revised application of a new proposal describes a comprehensive biochemical and biophysical investigation into the `DNA mimicry' of a recently discovered member of the Pentapeptide Repeat Protein (PRP) family of proteins. The atomic resolution structure of the MfpA PRP from Mycobacterium tuberculosis revealed a new protein fold; MfpA's right-handed 2-helical coils yield an elongated structure that is a remarkable mimic of the size, shape and electrostatic surface of DNA. That DNA mimicry is important to the biological role of MfpA is suggested by its ability to confer resistance to fluoro- quinolones by binding DNA gyrase thereby inhibiting its function. We will test the hypothesis that mimicry of the physical properties DNA by MfpA is the heart of its ability to confer drug resistance. Our long term goal is to understand the molecular mechanism by which MfpA and other PRP mediate antibiotic resistance and potentially regulate the enzymatic processing of DNA. MfpA will be developed as a model system for the exploration of DNA mimicry by this newly-discovered and widely-distributed class of proteins. Fluoroquinolones are extremely important antibiotics due to their efficacy against Gram- positive, Gram-negative and mycobacteria. Fluoroquinolones act on DNA gyrase with a unique mechanism of action. They are remarkable for their absence of toxicity and a therapeutic index that is the highest of all currently prescribed antibiotics. The rapid emergence, and spread, of transmissible forms of fluoroquinolone resistance due to the expression of the plasmid-encoded proteins threatens the clinical utility of these antibiotics. The proposed studies seek to understand how the physical properties of the Peptapeptide Repeat Proteins MfpA and Qnr generate resistance to fluoroquinolones. This understanding would provide new targets for therapeutics complementary to fluoroquinolone that would counter the PRP-mediated resistance. Conversely, an understanding of the mechanism by which these proteins function may allow the PRP fold to be used as a platform for the development of novel protein or peptide therapeutics.