A redox-controlled molecular switch revealed by the crystal structure of a bacterial heme PAS sensor.
PAS domains, which have been identified in over 1100 proteins from all three kingdoms of life, convert various input stimuli into signals that propagate to downstream components by modifying protein-protein interactions. One such protein is the Escherichia coli redox sensor, Ec DOS, a phosphodiesterase that degrades cyclic adenosine monophosphate in a redox-dependent manner. Here we report the crystal structures of the heme PAS domain of Ec DOS in both inactive Fe(3+) and active Fe(2+) forms at 1.32 and 1.9 A resolution, respectively. The protein folds into a characteristic PAS domain structure and forms a homodimer. In the Fe(3+) form, the heme iron is ligated to a His-77 side chain and a water molecule. Heme iron reduction is accompanied by heme-ligand switching from the water molecule to a side chain of Met-95 from the FG loop. Concomitantly, the flexible FG loop is significantly rigidified, along with a change in the hydrogen bonding pattern and rotation of subunits relative to each other. The present data led us to propose a novel redox-regulated molecular switch in which local heme-ligand switching may trigger a global "scissor-type" subunit movement that facilitates catalytic control.
Kurokawa
Hirofumi
H
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan. kurokawa@tagen.tohoku.ac.jp
Lee
Dong-Sun
DS
Watanabe
Miki
M
Sagami
Ikuko
I
Mikami
Bunzo
B
Raman
C S
CS
Shimizu
Toru
T
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D000242:Cyclic AMP / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006418:Heme / Q000737:chemistry; D006860:Hydrogen Bonding; D007501:Iron / Q000737:chemistry; D008024:Ligands; D008715:Methionine / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010727:Phosphoric Diester Hydrolases; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D006418:Heme; D008715:Methionine; D000242:Cyclic AMP; D007501:Iron; D010727:Phosphoric Diester Hydrolases; C464427:dosP protein, E coli