6ECI

Structure of the FAD binding protein MSMEG_5243 from Mycobacterium smegmatis

Summary for 6ECI

• Entry DOI: 10.2210/pdb6eci/pdb
• Descriptor: Pyridoxamine 5'-phosphate oxidase-related, FMN-binding protein, FLAVIN-ADENINE DINUCLEOTIDE, CHLORIDE ION, ... (4 entities in total)
• Functional Keywords: flavin adenine dinucleotide (fad) binding protein, flavin/deazaflavin dependent oxidoreductase (fdor), fad-binding protein
• Biological source: Mycobacterium smegmatis (strain ATCC 700084 / mc(2)155)
• Total number of polymer chains: 20
• Total formula weight: 307141.42

Authors

Ahmed, F.H.,Antoney, J.,Carr, P.D.,Jackson, C.J. (deposition date: 2018-08-07, release date: 2018-12-26, Last modification date: 2023-10-11)

Primary citation

Harold, L.K.,Antoney, J.,Ahmed, F.H.,Hards, K.,Carr, P.D.,Rapson, T.,Greening, C.,Jackson, C.J.,Cook, G.M.
FAD-sequestering proteins protect mycobacteria against hypoxic and oxidative stress.
J. Biol. Chem., 294:2903-2912, 2019

PubMed Abstract: The ability to persist in the absence of growth triggered by low oxygen levels is a critical process for the survival of mycobacterial species in many environmental niches. (), a gene of unknown function in , is up-regulated in response to hypoxia and regulated by DosRDosS/DosT, an oxygen- and redox-sensing two-component system that is highly conserved in mycobacteria. In this communication, we demonstrate that MSMEG_5243 is a lavin-uestering protein and henceforth refer to it as Fsq. Using an array of biochemical and structural analyses, we show that Fsq is a member of the diverse superfamily of flavin- and deazaflavin-dependent oxidoreductases (FDORs) and is widely distributed in mycobacterial species. We created a markerless deletion mutant of and demonstrate that is required for cell survival during hypoxia. Using deletion and overexpression, we found that enhances cellular resistance to hydrogen peroxide treatment. The X-ray crystal structure of Fsq, solved to 2.7 Å, revealed a homodimeric organization with FAD bound noncovalently. The Fsq structure also uncovered no potential substrate-binding cavities, as the FAD is fully enclosed, and electrochemical studies indicated that the Fsq:FAD complex is relatively inert and does not share common properties with electron-transfer proteins. Taken together, our results suggest that Fsq reduces the formation of reactive oxygen species (ROS) by sequestering free FAD during recovery from hypoxia, thereby protecting the cofactor from undergoing autoxidation to produce ROS. This finding represents a new paradigm in mycobacterial adaptation to hypoxia.

PubMed: 30567740
DOI: 10.1074/jbc.RA118.006237

Experimental method

X-RAY DIFFRACTION (2.69 Å)