Carp insulin: amino acid sequence, biological activity and structural properties

Area of Science:

• Biochemistry
• Endocrinology
• Comparative Biology

Background:

• Insulin structure and function are highly conserved across species.
• Variations in insulin sequences can impact biological activity and receptor binding.

Purpose of the Study:

• To determine the amino acid sequence of carp (Cyprinus carpio) insulin.
• To correlate carp insulin's sequence with its biological activity and structural properties.
• To compare carp insulin with mammalian insulins.

Main Methods:

• Amino acid sequencing of carp insulin.
• Biological activity assessment using a fat-cell assay.
• Structural analysis via circular dichroism and sedimentation analysis.

Main Results:

• Carp insulin's B chain is two residues longer at the N terminus compared to mammalian insulins.
• Key substitutions include proline at B21 and threonine at B22.
• Despite sequence differences, essential residues for activity and monomer association are conserved.
• Carp insulin showed a three-fold higher concentration for half-maximal response than porcine insulin, with an identical maximal response.
• Circular dichroism spectra indicated structural similarity to bovine insulin.
• Carp insulin successfully formed hexamers despite substitutions in the dimer-dimer contact region.

Conclusions:

• Carp insulin exhibits unique sequence features but maintains essential structural and functional characteristics of mammalian insulins.
• The observed sequence variations do not significantly impair its biological activity or ability to form functional hexamers.
• This study provides insights into insulin evolution and structure-function relationships.