Department of Biochemistry, University of Otago, Dunedin, New Zealand.
FEBS J. 2011 Jun;278(12):2034-43. doi: 10.1111/j.1742-4658.2011.08119.x. Epub 2011 May 17.
The peptide antibiotic bacitracin is widely used as an inhibitor of protein disulfide isomerase (PDI) to demonstrate the role of the protein-folding catalyst in a variety of molecular pathways. Commercial bacitracin is a mixture of at least 22 structurally related peptides. The inhibitory activity of individual bacitracin analogs on PDI is unknown. For the present study, we purified the major bacitracin analogs, A, B, H, and F, and tested their ability to inhibit the reductive activity of PDI by use of an insulin aggregation assay. All analogs inhibited PDI, but the activity (IC(50) ) ranged from 20 μm for bacitracin F to 1050 μm for bacitracin B. The mechanism of PDI inhibition by bacitracin is unknown. Here, we show, by MALDI-TOF/TOF MS, a direct interaction of bacitracin with PDI, involving disulfide bond formation between an open thiol form of the bacitracin thiazoline ring and cysteines in the substrate-binding domain of PDI.
多肽抗生素杆菌肽被广泛用作蛋白质二硫键异构酶（PDI）的抑制剂，以证明该蛋白折叠催化剂在多种分子途径中的作用。商业杆菌肽是至少 22 种结构相关肽的混合物。单个杆菌肽类似物对 PDI 的抑制活性是未知的。在本研究中，我们纯化了主要的杆菌肽类似物 A、B、H 和 F，并使用胰岛素聚集测定法测试了它们抑制 PDI 还原活性的能力。所有类似物都抑制了 PDI，但活性（IC（50））范围从杆菌肽 F 的 20μm 到杆菌肽 B 的 1050μm。杆菌肽抑制 PDI 的机制尚不清楚。在这里，我们通过 MALDI-TOF/TOF MS 显示，杆菌肽与 PDI 直接相互作用，涉及杆菌肽噻唑啉环的开放硫醇形式与 PDI 底物结合域中的半胱氨酸之间形成二硫键。
