Transferrins: iron release from lactoferrin.

Area of Science:

• Biochemistry
• Protein Chemistry
• Biophysical Chemistry

Background:

• Iron homeostasis is critical, with proteins like lactoferrin playing key roles.
• Understanding iron release mechanisms is vital for various biological and medical applications.
• Bovine lactoferrin is known for its iron-binding and antimicrobial properties.

Purpose of the Study:

• To investigate the in vitro mechanism of iron loss from bovine lactoferrin in acidic media.
• To determine the influence of different anions on the iron release process.
• To compare the iron release mechanism of lactoferrin with other iron-binding proteins like transferrins.

Main Methods:

• In vitro studies of iron loss from bovine lactoferrin.
• Investigation in acidic media (pH ≤ 3.5) with various anions (NO3-, Cl-, Br-, SO42-).
• Kinetic analysis of a four-step iron loss mechanism, including protonation and anion interactions.

Main Results:

• Bovine lactoferrin loses iron through a four-step mechanism involving conformational changes and protonation.
• The process is influenced by the presence and type of anions, with different rate constants and equilibrium constants observed.
• Unlike serum transferrin, lactoferrin requires prior conformational changes for iron release, explaining its stability in acidic conditions.

Conclusions:

• Bovine lactoferrin exhibits a unique iron loss mechanism in acidic media compared to iron transport proteins.
• The conformational stability of lactoferrin in acidic environments is attributed to its interdomain hydrogen bonds.
• These findings clarify why lactoferrin does not readily release iron in acidic conditions and is not involved in acidic endosome iron transport.