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Published on: October 1, 2015
Interaction of lactoferrin with ceruloplasmin
E T Zakharova1, M M Shavlovski, M G Bass
1Institute for Experimental Medicine, St. Petersburg, Russia.
Insights
Human lactoferrin (LF) binds to ceruloplasmin (CP) in serum, forming a 1:2 complex without major structural changes. This CP/LF complex is found in the body, and injected LF is incorporated into it.
Area of Science:
- Biochemistry
- Protein Interactions
- Human Physiology
Background:
- Lactoferrin (LF) is an iron-binding protein found in breast milk.
- Ceruloplasmin (CP) is a copper-containing oxidase present in human blood serum.
Purpose of the Study:
- To investigate the interaction between human lactoferrin (LF) and ceruloplasmin (CP).
- To characterize the resulting protein complex and its presence in the human body.
Main Methods:
- Polyacrylamide gel electrophoresis
- Immunodiffusion
- Gel filtration
- Affinity chromatography
- Near-UV circular dichroism spectroscopy
- Scatchard plot analysis
Main Results:
- Selective binding of LF to CP was confirmed.
- A CP:LF complex with a 1:2 molar stoichiometry was identified.
- Protein structures remained largely unchanged upon complex formation.
- The dissociation constant (K(d)) for the CP/LF complex was 1.8 x 10(-6) M.
- The CP/LF complex is present in various human bodily fluids.
- Injected human LF was found within the CP/LF complex in rat blood plasma and cleared within 5 hours.
Conclusions:
- Human lactoferrin and ceruloplasmin form a stable complex in serum.
- The CP/LF complex is a naturally occurring entity in the human body.
- LF's incorporation into CP influences its distribution and clearance in vivo.
Abstract:
When added to human blood serum, the iron-binding protein lactoferrin (LF) purified from breast milk interacts with ceruloplasmin (CP), a copper-containing oxidase. Selective binding of LF to CP is evidenced by the results of polyacrylamide gel electrophoresis, immunodiffusion, gel filtration, and affinity chromatography. The molar stoichiometry of CP:LF in the complex is 1:2. Near-uv circular dichroism spectra of the complex showed that neither of the two proteins undergoes major structural perturbations when interacting with its counterpart. K(d) for the CP/LF complex was estimated from Scatchard plot as 1.8 x 10(-6) M. The CP/LF complex is found in various fluids of the human body. Upon injection into rat of human LF, the latter is soon revealed within the CP/LF complex of the blood plasma, from where the human protein is substantially cleared within 5 h.
