Transferrin binding of Al3+ and Fe3+

Area of Science:

• Biochemistry
• Toxicology
• Protein-metal interactions

Background:

• Understanding Al3+-induced diseases necessitates identifying its blood carrier.
• Al3+ toxicity is a concern in various health conditions.

Purpose of the Study:

• To identify the primary blood carrier of aluminum (Al3+).
• To quantify the binding affinity of Al3+ to transferrin.
• To compare Al3+ binding with iron (Fe3+) binding to transferrin.

Main Methods:

• Quantitative analysis of Al3+ binding to transferrin.
• Spectroscopic methods to determine metal ion binding stability constants.
• Comparison of Al3+ and Fe3+ binding constants.

Main Results:

• Transferrin is the strongest Al3+ binder in blood plasma.
• Stability constants for Al3+-transferrin binding were determined (log K1 = 12.9, log K2 = 12.3).
• Al3+ binding constants are weaker than Fe3+ binding constants, suggesting different coordination.

Conclusions:

• Transferrin is the ultimate carrier of Al3+ in the blood.
• The weaker binding of Al3+ compared to Fe3+ suggests steric limitations in coordination.
• This finding is crucial for understanding Al3+ transport and toxicity.