Journal of Protein Chemistry

, Volume 19, Issue 3, pp 239–248

Heme Binding by Hemopexin: Evidence for Multiple Modes of Binding and Functional Implications

  • Natalia Shipulina
  • Ann Smith
  • William T. Morgan
Article

DOI: 10.1023/A:1007016105813

Cite this article as:
Shipulina, N., Smith, A. & Morgan, W.T. J Protein Chem (2000) 19: 239. doi:10.1023/A:1007016105813

Abstract

Hemopexin binds 1 mol of heme per mol with high affinity (Kd < 1 pM) in a low-spin complex and acts as a transport vehicle for the heme. Circular dichroism (CD) spectroscopy was used to examine the heme environment in the ferri-, ferro-, and CO-ferro complexes of four iron tetrapyrroles [meso-, proto-, deutero-, and (2-vinyl, 4-hydroxymethyl)-deutero-heme] with three species (human, rabbit, and rat) of hemopexin. All ferri-heme-hemopexin complexes exhibit a band of positive ellipticity near the Soret maximum, except for the human ferri-protoheme hemopexin complex, which has a bisignate spectrum. The ferro-heme and CO-ferro-heme complexes display a variety of spectra, demonstrating redox- and ligand-linked shifts in conformation that alter the environment of the heme. The rabbit mesoheme-N-domain complexes have absorbance spectra almost indistinguishable from those of intact hemopexin, but present CD spectra that are distinctly different. However, adding the C-domain to mesoheme-N-domain restores most of the CD characteristics of the intact hemopexin complexes.

Hemopexin heme circular dichroism spectroscopy CO-binding 

Copyright information

© Plenum Publishing Corporation 2000

Authors and Affiliations

  • Natalia Shipulina
    • 1
  • Ann Smith
    • 1
  • William T. Morgan
    • 2
  1. 1.Division of Molecular Biology and Biochemistry, School of Biological SciencesUniversity of Missouri-Kansas CityKansas City
  2. 2.Division of Molecular Biology and Biochemistry, School of Biological SciencesUniversity of Missouri-Kansas CityKansas City