A molecular model for the tumour-associated antigen, p97, suggests a Zn-binding function.

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Evolution

Background:

• Melanotransferrin (p97) is a member of the transferrin superfamily.
• Understanding its structure and function is crucial for comparative analysis within the superfamily.

Purpose of the Study:

• To compare the primary structure of melanotransferrin (p97) with other transferrin superfamily members.
• To model the molecular structure of p97 based on existing transferrin crystal structures.
• To identify unique structural and functional characteristics of p97.

Main Methods:

• Comparative analysis of primary protein structures.
• Molecular modeling utilizing crystal structures of related proteins (diferric rabbit serum transferrin).
• Identification of specific amino acid substitutions and conserved motifs.

Main Results:

• Significant amino acid substitutions in p97 are concentrated in the C-lobe iron-binding cleft and interlobe contact region.
• A zinc-binding consensus sequence, characteristic of metallopeptidases, was identified in the N-terminal lobe.
• A specific glutamic acid residue (Glu-394) in the C-terminal lobe can complete a potential thermolysin-like zinc-binding site.

Conclusions:

• Melanotransferrin (p97) exhibits unique structural features compared to other transferrins.
• The identified regions suggest a potential for zinc-binding in p97, a characteristic not previously recognized in the transferrin superfamily.
• This unique zinc-binding capability may confer novel functions to melanotransferrin.