Structural basis for novel delta-regioselective heme oxygenation in the opportunistic pathogen Pseudomonas aeruginosa.
The Gram-negative bacterium Pseudomonas aeruginosa contains a heme oxygenase (pa-HO) that primarily oxygenates the delta-meso heme carbon [Caignan, G. A., Deshmukh, R., Wilks, A., Zeng, Y., Huang, H. W., Moenne-Loccoz, P., Bunce, R. A., Eastman, M. A., and Rivera, M. (2002) J. Am. Chem. Soc. 124, 14879-14892]. This differs from other previously characterized heme oxygenases, which display regioselectivity for the alpha-meso heme carbon. Here we report the crystal structure of pa-HO at 1.60 A resolution and compare it to the 1.50 A structure of nm-HO from Neisseria meningitidis [Schuller, D. J., Zhu, W., Stojiljkovic, I., Wilks, A., and Poulos, T. L. (2001) Biochemistry 40, 11552-11558]. The crystal structure of pa-HO maintains the same overall fold as other bacterial and mammalian heme oxygenases, including a conserved network of hydrogen-bonded solvent molecules important for dioxygen activation. The novel delta-regioselectivity of heme oxygenation observed by pa-HO is due to the heme being rotated by approximately 100 degrees, which places the delta-meso heme carbon in the same position as the alpha-meso heme carbon in other heme oxygenases. The main interaction in pa-HO that stabilizes the unique heme orientation is a salt bridge between Lys132 and the heme 7-propionate, as well as hydrophobic contacts involving Leu29, Val33, and Phe189 with the heme methyl and vinyl groups.
Friedman
Jonathan
J
Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA.
Lad
Latesh
L
Li
Huiying
H
Wilks
Angela
A
Poulos
Thomas L
TL
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006418:Heme / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006860:Hydrogen Bonding; D006900:Hydroxylation; D009345:Neisseria meningitidis / Q000201:enzymology; D009894:Opportunistic Infections / Q000382:microbiology; D011422:Propionates / Q000737:chemistry; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D051381:Rats; D040681:Structural Homology, Protein; D013379:Substrate Specificity
D001426:Bacterial Proteins; D011422:Propionates; D006418:Heme; D006419:Heme Oxygenase (Decyclizing)