Wu Gang, Liu Wen, Berka Vladimir, Tsai Ah-Lim
Division of Hematology, Department of Internal Medicine, The University of Texas - McGovern Medical School, 6431 Fannin Street, Houston, TX, 77030, USA.
Center for Infectious and Inflammatory Diseases, Texas A&M University - Health Science Center, 2121 West Holcombe Blvd, Houston, TX, 77030, USA.
Biochimie. 2017 Sep;140:82-92. doi: 10.1016/j.biochi.2017.06.014. Epub 2017 Jun 26.
To delineate the commonalities and differences in gaseous ligand discrimination among the heme-based sensors with Heme Nitric oxide/OXygen binding protein (H-NOX) scaffold, the binding kinetic parameters for gaseous ligands NO, CO, and O, including K, k, and k, of Shewanella oneidensis H-NOX (So H-NOX) were characterized in detail in this study and compared to those of previously characterized H-NOXs from Clostridium botulinum (Cb H-NOX), Nostoc sp. (Ns H-NOX), Thermoanaerobacter tengcongensis (Tt H-NOX), Vibrio cholera (Vc H-NOX), and human soluble guanylyl cyclase (sGC), an H-NOX analogue. The K(NO) and K(CO) of each bacterial H-NOX or sGC follow the "sliding scale rule"; the affinities of the bacterial H-NOXs for NO and CO vary in a small range but stronger than those of sGC by at least two orders of magnitude. On the other hand, each bacterial H-NOX exhibits different characters in the stability of its 6c NO complex, reactivity with secondary NO, stability of oxyferrous heme and autoxidation to ferric heme. A facile access channel for gaseous ligands is also identified, implying that ligand access has only minimal effect on gaseous ligand selectivity of H-NOXs or sGC. This comparative study of the binding parameters of the bacterial H-NOXs and sGC provides a basis to guide future new structural and functional studies of each specific heme sensor with the H-NOX protein fold.
为了阐明具有血红素一氧化氮/氧气结合蛋白（H-NOX）支架的基于血红素的传感器在气体配体识别方面的共性和差异，本研究详细表征了希瓦氏菌H-NOX（So H-NOX）对气体配体NO、CO和O的结合动力学参数，包括K、k和k，并与先前表征的来自肉毒梭菌（Cb H-NOX）、念珠藻属（Ns H-NOX）、腾冲嗜热厌氧菌（Tt H-NOX）、霍乱弧菌（Vc H-NOX）的H-NOX以及人可溶性鸟苷酸环化酶（sGC，一种H-NOX类似物）的参数进行了比较。每种细菌H-NOX或sGC的K(NO)和K(CO)遵循“滑动尺度规则”；细菌H-NOX对NO和CO的亲和力在小范围内变化，但比sGC至少强两个数量级。另一方面，每种细菌H-NOX在其6c NO复合物的稳定性、与二级NO的反应性、亚铁血红素的稳定性以及自氧化为高铁血红素方面表现出不同的特性。还确定了一条气体配体的便捷通道，这意味着配体进入对H-NOX或sGC的气体配体选择性影响极小。对细菌H-NOX和sGC结合参数的这项比较研究为指导未来对具有H-NOX蛋白折叠的每种特定血红素传感器进行新的结构和功能研究提供了基础。
