Binding of oxygen and carbon monoxide to a heme-regulated phosphodiesterase from Escherichia coli. Kinetics and infrared spectra of the full-length wild-type enzyme, isolated PAS domain, and Met-95 mutants.
The heme-regulated phosphodiesterase, Ec DOS, is a redox sensor that uses the heme in its PAS domain to regulate catalysis. The rate of O(2) association (k(on)) with full-length Ec DOS is extremely slow at 0.0019 microM(-1) s(-1), compared with >9.5 microM(-1) s(-1) for 6-coordinated globin-type hemoproteins, as determined by the stopped-flow method. This rate is dramatically increased (up to 16-fold) in the isolated heme-bound PAS domain. Dissociation constants (K(d)) calculated from the kinetic parameters are 340 and 20 microm for the full-length wild-type enzyme and its isolated PAS domain, respectively. Mutations at Met-95 in the isolated PAS domain, which may be a heme axial ligand in the Fe(II) complex, lead to a further increase in the k(on) value by more than 30-fold, and consequently, a decrease in the K(d) value to less than 1 microM. The k(on) value for CO binding to the full-length wild-type enzyme is also very low (0.00081 microM(-1) s(-1)). The kinetics of CO binding to the isolated PAS domain and its mutants are similar to those observed for O(2). However, the K(d) values for CO are considerably lower than those for O(2).
Taguchi
Sue
S
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
Matsui
Toshitaka
T
Igarashi
Jotaro
J
Sasakura
Yukie
Y
Araki
Yasuyuki
Y
Ito
Osamu
O
Sugiyama
Shunpei
S
Sagami
Ikuko
I
Shimizu
Toru
T
D002248:Carbon Monoxide / Q000737:chemistry*; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D008027:Light; D008715:Methionine / Q000737:chemistry; D009154:Mutation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010727:Phosphoric Diester Hydrolases; D017434:Protein Structure, Tertiary; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors
D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D006418:Heme; D002248:Carbon Monoxide; D008715:Methionine; D010727:Phosphoric Diester Hydrolases; C464427:dosP protein, E coli; D010100:Oxygen