Myeloperoxidase (MPO), an important enzyme in the oxygen-dependent host defense system of human polymorphonuclear leukocytes, utilizes hydrogen peroxide to catalyze the production of hypochlorous acid, an oxidizing bactericidal agent. While MPO shows significant sequence homology with other peroxidases and this homology is particularly striking among the active site residues, MPO exhibits unusual spectral features and the unique ability to catalyze the oxidation of chloride ions. We have investigated the MPO active site with x-ray absorption and resonance Raman spectroscopies at neutral pH and also at the physiological acidic pH and have compared these results with those of horseradish peroxidase. The MPO heme environment was found to be inhomogeneous. At pH 7.5, the iron heme active site is 6-coordinate where the distal ligand is likely oxygen or nitrogen, but not sulfur. The heme is distorted compared to HRP, other peroxidases, and heme compounds, but at pH3, the distal ligand is lost and the heme is less distorted. HRP also loses its loosely associated distal water at this pH, but little change in heme distortion is observed. This change suggests that loss of the distal ligand in MPO releases stress on the heme which may facilitate binding of chloride ion.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
5P41RR001633-14
Application #
5223485
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
14
Fiscal Year
1996
Total Cost
Indirect Cost
Vongsvivut, Jitraporn; Fernandez, Jason; Ekgasit, Sanong et al. (2004) Characterization of supported cylinder-planar germanium waveguide sensors with synchrotron infrared radiation. Appl Spectrosc 58:143-51
Masip, Lluis; Pan, Jonathan L; Haldar, Suranjana et al. (2004) An engineered pathway for the formation of protein disulfide bonds. Science 303:1185-9
Huang, Raymond Y; Miller, Lisa M; Carlson, Cathy S et al. (2003) In situ chemistry of osteoporosis revealed by synchrotron infrared microspectroscopy. Bone 33:514-21
Rashidzadeh, Hassan; Khrapunov, Sergei; Chance, Mark R et al. (2003) Solution structure and interdomain interactions of the Saccharomyces cerevisiae ""TATA binding protein"" (TBP) probed by radiolytic protein footprinting. Biochemistry 42:3655-65
Uchida, Takeshi; Takamoto, Keiji; He, Qin et al. (2003) Multiple monovalent ion-dependent pathways for the folding of the L-21 Tetrahymena thermophila ribozyme. J Mol Biol 328:463-78
Taylor, Colleen M; Watton, Stephen P; Bryngelson, Peter A et al. (2003) Inner-sphere complexation of cobalt(II) 2,9-dimethyl-1,10-phenanthroline ([Co(neo)]2+) with commercial and sol-gel derived silica gel surfaces. Inorg Chem 42:312-20
Dewan, John C; Feeling-Taylor, Angela; Puius, Yoram A et al. (2002) Structure of mutant human carbonmonoxyhemoglobin C (betaE6K) at 2.0 A resolution. Acta Crystallogr D Biol Crystallogr 58:2038-42
Kiselar, J G; Maleknia, S D; Sullivan, M et al. (2002) Hydroxyl radical probe of protein surfaces using synchrotron X-ray radiolysis and mass spectrometry. Int J Radiat Biol 78:101-14
Swisher, Jennifer F; Su, Linhui J; Brenowitz, Michael et al. (2002) Productive folding to the native state by a group II intron ribozyme. J Mol Biol 315:297-310
Dhavan, Gauri M; Crothers, Donald M; Chance, Mark R et al. (2002) Concerted binding and bending of DNA by Escherichia coli integration host factor. J Mol Biol 315:1027-37

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