From the Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205 and.
the Departments of Medicine and Medical Microbiology and Immunology, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53726.
J Biol Chem. 2019 Feb 22;294(8):2700-2713. doi: 10.1074/jbc.RA118.007095. Epub 2018 Dec 28.
Copper-only superoxide dismutases (SODs) represent a new class of SOD enzymes that are exclusively extracellular and unique to fungi and oomycetes. These SODs are essential for virulence of fungal pathogens in pulmonary and disseminated infections, and we show here an additional role for copper-only SODs in promoting survival of fungal biofilms. The opportunistic fungal pathogen expresses three copper-only SODs, and deletion of one of them, , eradicated candidal biofilms on venous catheters in a rodent model. Fungal copper-only SODs harbor an irregular active site that, unlike their Cu,Zn-SOD counterparts, contains a copper co-factor unusually open to solvent and lacks zinc for stabilizing copper binding, making fungal copper-only SODs highly vulnerable to metal chelators. We found that unlike mammalian Cu,Zn-SOD1, SOD5 indeed rapidly loses its copper to metal chelators such as EDTA, and binding constants for Cu(II) predict that copper-only SOD5 has a much lower affinity for copper than does Cu,Zn-SOD1. We screened compounds with a variety of indications and identified several metal-binding compounds, including the ionophore pyrithione zinc (PZ), that effectively inhibit SOD5 but not mammalian Cu,Zn-SOD1. We observed that PZ both acts as an ionophore that promotes uptake of toxic metals and inhibits copper-only SODs. The pros and cons of a vulnerable active site for copper-only SODs and the possible exploitation of this vulnerability in antifungal drug design are discussed.
铜-only 超氧化物歧化酶（SOD）代表了一类新的 SOD 酶，它们只存在于真菌和卵菌中，且为细胞外酶。这些 SOD 对于肺部和全身性真菌感染中真菌病原体的毒力至关重要，我们在这里还展示了铜-only SOD 促进真菌生物膜存活的另一个作用。机会性真菌病原体 表达三种铜-only SOD，其中一种铜-only SOD（ ）缺失后，可在啮齿动物模型中消除静脉导管上的念珠菌生物膜。真菌铜-only SOD 具有不规则的活性部位，与 Cu,Zn-SOD 不同，其含有一个铜辅因子，异常开放于溶剂中，并且缺乏稳定铜结合的锌，这使得真菌铜-only SOD 极易受到金属螯合剂的影响。我们发现，与哺乳动物 Cu,Zn-SOD1 不同， SOD5 确实会迅速将其铜离子释放到金属螯合剂如 EDTA 中，Cu(II)的结合常数表明铜-only SOD5 对铜的亲和力远低于 Cu,Zn-SOD1。我们筛选了具有多种适应症的化合物，并确定了几种金属结合化合物，包括离子载体吡啶硫酮锌（PZ），它可以有效抑制 SOD5，但不抑制哺乳动物 Cu,Zn-SOD1。我们观察到 PZ 既可以作为促进有毒金属摄取的离子载体，又可以抑制铜-only SOD。本文讨论了铜-only SOD 脆弱的活性部位的优缺点，以及在抗真菌药物设计中利用这一脆弱性的可能性。
