Use of iron-meso-tetra-(4-sulfonatophenyl)-porphine (FeTPPS) to examine hemopexin-mediated heme transport
Hemopexin (HPX) alters conformation upon binding heme as shown by circular dichroism (CD) while FeTPPS binds without changes in the CD spectrum . Therefore, FeTPPS was used to examine the importance of changes in HPX conformation for receptor binding and for HPX-mediated heme transport. FeTPPS-HPX binds to the HPX receptor on mouse hepatoma Hepa cells but with lower affinity then heme-HPX. Incubation of cells with 50 nM heme-/sup 125/I-HPX after 2.5 ..mu..M heme- or FeTPPS-HPX decreased binding from 0.34 pmol/mg protein to 0.10 and 0.27, respectively. Preincubation with 2.5 ..mu..M apoHPX reduced binding to the same extent as FeTPPS-HPX indicating that certain conformational changes in HPX increase the affinity of its receptor. Interestingly, FeTPPS-HPX inhibited heme uptake more effectively than heme-HPX. Preincubation of cells with 2.5 ..mu..M heme- or FeTPPS-HPX decreased /sup 55/Feheme uptake from /sup 55/Feheme-HPX (500 nM) by 28% and 70%, respectively; heme or FeTPPS alone had no effect. After incubation with 500 nM /sup 55/Feheme-HPX or /sup 55/FeTPPS-HPX for up to 30 minutes at 37/sup 0/C, /sup 55/Feheme was associated with the plasma-membrane and intracellular compartments but /sup 55/FeTPPs remained with the plasma membrane. FeTPPS presented to the cells as a complex with HPX inhibits HPX-mediated heme uptake by blocking events after heme-HPX binds to its receptor but needed for heme transport.
- Research Organization:
- Louisiana State Univ. Medical Center, New Orleans
- OSTI ID:
- 5022173
- Report Number(s):
- CONF-8606151-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
Similar Records
Cyanide binding to human plasma heme-hemopexin: A comparative study
Characterization of imidazole binding sites labeled by /sup 3/H-p-aminoclonidine in the bovine ventrolateral medulla (VLM)
Related Subjects
HEME
MEMBRANE TRANSPORT
PROTEINS
RECEPTORS
BIOCHEMICAL REACTION KINETICS
AFFINITY
CELL MEMBRANES
IODINE 125
IRON
IRON 55
MICE
TRACER TECHNIQUES
TUMOR CELLS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-ODD NUCLEI
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
IRON ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
METALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
TRANSITION ELEMENTS
VERTEBRATES
YEARS LIVING RADIOISOTOPES
550201* - Biochemistry- Tracer Techniques