Heme-nitric oxide/oxygen binding (H-NOX) proteins are a group of hemoproteins that bind diatomic gas ligands such as nitric oxide (NO) and oxygen (O₂). H-NOX proteins typically regulate histidine kinases (HK) located within the same operon. It has been reported that NO-bound H-NOXs inhibit cognate histidine kinase autophosphorylation in bacterial H-NOX/HK complexes; however, a detailed mechanism of NO-mediated regulation of the H-NOX/HK activity remains unknown. In this study, the binding interface of Vibrio cholerae (Vc) H-NOX/HK complex was characterized by hydrogen/deuterium exchange mass spectrometry (HDX-MS) and further validated by mutagenesis, leading to a new model for NO-dependent kinase inhibition. A conformational change in Vc H-NOX introduced by NO generates a new kinase-binding interface, thus locking the kinase in an inhibitory conformation.

中文翻译：

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氢/氘交换质谱法绘制霍乱弧菌中H-NOX / HK结合界面的图谱

血红一氧化氮/氧结合（H-NOX）蛋白是一组结合双原子气体配体（如一氧化氮（NO）和氧（O ₂））的血蛋白。H-NOX蛋白通常调节位于同一操纵子内的组氨酸激酶（HK）。据报道，NO结合的H-NOXs抑制细菌H-NOX / HK复合物中的同源组氨酸激酶自磷酸化。然而，NO介导的H-NOX / HK活性调节的详细机制仍是未知的。在这项研究中，霍乱弧菌（Vc）H-NOX / HK复合物的结合界面已通过氢/氘交换质谱（HDX-MS）进行了表征，并通过诱变得到进一步验证，从而产生了一种新的NO依赖性激酶抑制模型。Vc的构象变化 NO引入的H-NOX产生新的激酶结合界面，从而将激酶锁定在抑制性构象中。