STRUCTURAL STUDIES OF REDOX ENZYMES AND MEDICALLY IMPORTANT SERINE PROTEASES

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 研究中心，而研究中心不一定是研究者所在的机构。 这是一个为期2年的生物大分子结构研究APS束时间的建议。它侧重于哺乳动物丝氨酸蛋白酶凝血酶，两个黄素蛋白氧化还原系统和电子转移（ET）突变体的铜氧还蛋白，接受电子从醌酶。 人凝血酶催化纤维蛋白原蛋白水解转化为血凝块的主要成分纤维蛋白。将确定这些蛋白质的几种突变形式以及各种酶-底物和酶-抑制剂复合物的结构，以阐明它们的作用模式。这些研究将扩展到在几个方面与人酶不同的鼠酶。 异四聚体肌氨酸氧化酶（TSOX）是一种氧化还原黄素蛋白，分离自嗜麦芽假单胞菌，含有FAD、FMN并结合四氢叶酸（THF）。TSOX催化肌氨酸（N-甲基甘氨酸）氧化为亚胺中间体和还原的FAD;在第二步中，亚胺中间体与THF结合形成5，10-亚甲基-THF。两个催化位点相隔约35埃。FAD被ET再氧化成FMN，然后后者还原分子氧产生过氧化物。 第二种氧化还原黄素酶是nikD，其催化Streptomyces tendae中尼可霉素抗生素生物合成的早期步骤。它是一种含有FAD的45 kDa单体;其结构已知有两种不同的构象。将对其突变体的结构进行研究。 Amicyanin是一种9 kDa的蓝色铜蛋白，可接受来自副球菌中甲胺脱氢酶（MADH）的电子。几种amicyanin突变体的氧化还原特性显示出与野生型蛋白质的显着差异，这些突变体的原子分辨率结构是已知的。将研究这些突变体与MADH的ET复合物的晶体。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is a 2-year proposal for APS beam time for structural studies of biological macromolecules. It focuses on the mammalian serine protease thrombin, on two flavoprotein redox systems and on electron transfer (ET) mutants of a cupredoxin that accepts electrons from a quinoenzyme. Human thrombin catalyzes the proteolytic conversion of fibrinogen to fibrin, the major component of a blood clot. The structures of several mutant forms of these proteins, as well as of various enzyme-substrate and enzyme-inhibitor complexes will be determined in order to elucidate their modes of action. These studies will be extended to the murine enzyme which differs in several respects from the human enzyme. One of the redox flavoproteins, heterotetrameric sarcosine oxidase (TSOX), isolated from Pseudomonas maltophilia, contains FAD, FMN and binds tetrahydrofolate (THF). TSOX catalyzes the oxidation of sarcosine (N-methyl glycine) to an imine intermediate and reduced FAD; in a second step the imine intermediate combines with THF to form 5,10-methylene-THF. The two catalytic sites are separated by about 35 A. The FAD is reoxidized by ET to FMN and the latter then reduces molecular oxygen to yield peroxide. A second redox flavoenzyme is nikD, which catalyzes an early step in the biosynthesis of nikkomycin antibiotics in Streptomyces tendae. It is a monomer of 45 kDa containing FAD; its structure is known in two distinct conformation. Structures of its mutants will be studied. Amicyanin is a blue copper protein of 9 kDa that accepts electrons from methylamine dehydrogenase (MADH) in Paracoccus denitrificans. The redox properties of several amicyanin mutants show significant differences from the wild type protein; atomic resolution structures of these mutants are known. Crystals of ET complexes of these mutants with MADH will be studied.