Interdomain Interactions within the Two-Component Heme-Based Sensor DevS from Mycobacterium tuberculosis

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• 作者：Erik T. Yukl ; Alexandra Ioanoviciu ; Paul R. Ortiz de Montellano ; Pierre Mo&euml ; nne-Loccoz
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：August 28, 2007
• 年：2007
• 卷：46
• 期：34
• 页码：9728 - 9736
• 全文大小：285K
• 年卷期：v.46,no.34(August 28, 2007)
• ISSN：1520-4995

文摘

DevS is the sensor of the DevS-DevR two-component regulatory system of Mycobacteriumtuberculosis. This system is thought to be responsible for initiating entrance of this bacterium into thenonreplicating persistent state in response to NO and anaerobiosis. DevS is modular in nature and consistsof two N-terminal GAF domains and C-terminal histidine kinase and ATPase domains. The first GAFdomain (GAF A) binds heme, and this cofactor is thought to be responsible for sensing environmentalstimuli, but the function of the second GAF domain (GAF B) is unknown. Here we report the RRcharacterization of full-length DevS (FL DevS) as well as truncated proteins consisting of the single GAFA domain (GAF A DevS) and both GAF domains (GAF A/B) in both oxidation states and bound to theexogenous ligands CO, NO, and O₂. The results indicate that the GAF B domain increases the specificitywith which the distal heme pocket of the GAF A domain interacts with CO and NO as opposed to O₂.Specifically, while two comparable populations of CO and NO adducts are observed in GAF A DevS,only one of these two conformers is present in significant concentration in the GAF A/B and FL DevSproteins. In contrast, hydrogen bond interactions at the bound oxygen in the oxy complexes are conservedin all DevS constructs. The comparison of the data obtained with the O₂ complexes with those of the COand NO complexes suggests a model for ligand discrimination which relies on a specific hydrogen-bonding network with bound O₂. It also suggests that interactions between the two GAF domains areresponsible for transduction of structural changes at the heme domain that accompany ligand binding/dissociation to modulate activity at the kinase domain.