Human biliverdin reductase is a leucine zipper-like DNA-binding protein and functions in transcriptional activation of heme oxygenase-1 by oxidative stress.
Human biliverdin reductase (hBVR) is a serine/threonine kinase that catalyzes reduction of the heme oxygenase (HO) activity product, biliverdin, to bilirubin. A domain of biliverdin reductase (BVR) has primary structural features that resemble leucine zipper proteins. A heptad repeat of five leucines (L(1)--L(5)), a basic domain, and a conserved alanine characterize the domain. In hBVR, a lysine replaces L(3). The secondary structure model of hBVR predicts an alpha-helix-turn-beta-sheet for this domain. hBVR translated by the rabbit reticulocyte lysate system appears on a nondenaturing gel as a single band with molecular mass of approximately 69 kDa. The protein on a denaturing gel separates into two anti-hBVR immunoreactive proteins of approximately 39.9 + 34.6 kDa. The dimeric form, but not purified hBVR, binds to a 100-mer DNA fragment corresponding to the mouse HO-1 (hsp32) promoter region encompassing two activator protein (AP-1) sites. The specificity of DNA binding is suggested by the following: (a) hBVR does not bind to the same DNA fragment with one or zero AP-1 sites; (b) a 56-bp random DNA with one AP-1 site does not form a complex with hBVR; (c) in vitro translated HO-1 does not interact with the 100-mer DNA fragment with two AP-1 sites; (d) mutation of Lys(143), Leu(150), or Leu(157) blocks both the formation of the approximately 69-kDa specimens and hBVR DNA complex formation; and (e) purified preparations of hBVR or hHO-1 do not bind to DNA with two AP-1 sites. The potential significance of the AP-1 binding is suggested by the finding that the response of HO-1, in COS cells stably transfected with antisense hBVR, with 66% reduced BVR activity, to superoxide anion (O(2)()) formed by menadione is attenuated, whereas induction by heme is not affected. We propose a role for BVR in the signaling cascade for AP-1 complex activation necessary for HO-1 oxidative stress response.
Ahmad
Zulfiqar
Z
Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
Salim
Mohammad
M
Maines
Mahin D
MD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000502:physiology*; D019281:Dimerization; D006418:Heme / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics*; D051547:Heme Oxygenase-1; D006801:Humans; D016350:Leucine Zippers; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000737:chemistry / Q000502:physiology*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D014176:Protein Biosynthesis; D015534:Trans-Activators / Q000502:physiology*; D024483:Vitamin K 3 / Q000494:pharmacology
D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D015534:Trans-Activators; D006418:Heme; D024483:Vitamin K 3; D004247:DNA; D010088:Oxidoreductases; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019789:biliverdin reductase