Isolation and Characterization of a cDNA from the Rat Brain that Encodes Hemoprotein Heme Oxygenase-3

Authors

  • William K. Mccoubrey Jr,

    1. University of Rochester School of Medicine and Dentistry, Departments of Biochemistry/Biophysics and Environmental Medicine, Rochester, USA
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  • T. J. Huang,

    1. University of Rochester School of Medicine and Dentistry, Departments of Biochemistry/Biophysics and Environmental Medicine, Rochester, USA
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  • Mahin D. Maines

    Corresponding author
    1. University of Rochester School of Medicine and Dentistry, Departments of Biochemistry/Biophysics and Environmental Medicine, Rochester, USA
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M. D. Maines, University of Rochester School of Medicine and Dentistry, Department of Biochemistry/Biophysics and Environmental Medicine, 601 Elmwood Avenue, Rochester, NY 14642, USA
Fax:+1 716 256 2591.
E-mail;MDMS@bphvax.biophysics.rochester.edu

Abstract

Two isozymes of heme oxygenase (HO), HO-1 or HSP32 and the constitutive form HO-2, have been characterized to date. We report the discovery of a third protein species and refer to it as HO-3. HO-3 is the product of a single transcript of ≈2.4 kb and can encode a protein of ≈33 kDa. The HO-3 transcript is found in the spleen, liver, thymus, prostate, heart, kidney, brain and testis and is the product of a single-copy gene. The predicted amino acid structure of HO-3 differs from both HO-1 (HSP32) and HO-2 but is closely related to HO-2 (≈90%). Escherichia coli expressed and purified HO-3 protein does not cross react with polyclonal antibodies to either rat HO-1 or HO-2, is a poor heme catalyst, and displays hemoprotein spectral characteristics. The predicted protein has two heme regulatory motifs that may be involved in heme binding. These motifs and the hemoprotein nature of HO-3 suggest a potential regulatory role for the protein in cellular processes which are heme-dependent.

Abbreviations
HO

heme oxygenase

HRM

heme regulatory motif

STI

soybean trypsin inhibitor

UTR

untranslated region

IPTG

isopro-pry1 β-D-thiogalactoside

Ancillary