A structural framework for understanding the multifunctional character of lactoferrin.

Area of Science:

• Biochemistry
• Structural Biology
• Immunology

Background:

• Lactoferrin (Lf) is a multifunctional iron-binding protein found in mammalian secretions and immune cells.
• Its three-dimensional structure, determined in 1987, provided the first atomic view of a transferrin family member.
• Lf's complex biology necessitates a deep understanding of its structure-function relationships.

Purpose of the Study:

• To review how structural knowledge has advanced the understanding of lactoferrin function.
• To identify areas of lactoferrin biology that require further investigation.
• To explore the functional implications of Lf's conserved internal and variable external structures.

Main Methods:

• Review of existing structural and functional studies on lactoferrin.
• Analysis of conserved and variable regions of the lactoferrin molecule.
• Examination of the role of iron binding, N-terminal domains, and glycosylation in Lf function.

Main Results:

• Lf possesses highly conserved internal iron-binding sites crucial for iron scavenging and iron-status-dependent dynamics.
• The external structure of Lf is variable, with the cationic N-terminus and lactoferricin domain playing roles in antibacterial activity, DNA binding, and protein complex formation.
• Species-specific variations in Lf surface structure may lead to functional differences.

Conclusions:

• Structural insights have elucidated key aspects of lactoferrin's iron-binding and related functions.
• The variable surface regions, particularly the N-terminus, are critical for diverse biological activities.
• Re-evaluation of glycosylation's role in lactoferrin-pathogen interactions is warranted given new evidence.