Rational Design of α‑Helix-Stabilized
Exendin‑4 Analogues
- Publication date
- Publisher
Abstract
Exendin-4 (Ex4) is a potent glucagon-like
peptide-1 receptor agonist,
a drug regulating the plasma glucose level of patients suffering from
type 2 diabetes. The molecule’s poor solubility and its readiness
to form aggregates increase the likelihood of unwanted side effects.
Therefore, we designed Ex4 analogues with improved structural characteristics
and better water solubility. Rational design was started from the
parent 20-amino acid, well-folded Trp cage (TC) miniprotein and involved
the step-by-step N-terminal elongation of the TC head, resulting in
the 39-amino acid Ex4 analogue, E19. Helical propensity coupled to
tertiary structure compactness was monitored and quantitatively analyzed
by electronic circular dichroism and nuclear magnetic resonance (NMR)
spectroscopy for the 14 peptides of different lengths. Both <sup>15</sup>N relaxation- and diffusion-ordered NMR measurements were established
to investigate the inherent mobility and self-association propensity
of Ex4 and E19. Our designed E19 molecule has the same tertiary structure
as Ex4 but is more helical than Ex4 under all studied conditions;
it is less prone to oligomerization and has preserved biological activity.
These conditions make E19 a perfect lead compound for further drug
discovery. We believe that this structural study improves our understanding
of the relationship between local molecular features and global physicochemical
properties such as water solubility and could help in the development
of more potent Ex4 analogues with improved pharmacokinetic properties