PDBsum entry 6p4z

Hormone

PDB id: 6p4z

Contents

Protein chains

21 a.a.

30 a.a.

26 a.a.

Metals

_GD

_CO ×2

_CL

Waters ×48

References listed in PDB file

Key reference

• Title: Insulin hexamer-Caged gadolinium ion as mri contrast-O-Phore.
• Authors: S.K.Taylor, T.H.Tran, M.Z.Liu, P.E.Harris, Y.Sun, S.R.Jambawalikar, L.Tong, M.N.Stojanovic.
• Ref.: Chemistry, 2018, 24, 10646-10652. [DOI no: 10.1002/chem.201801388]
• PubMed id: 29873848

Abstract

High-relaxivity protein-complexes of Gd^III are being pursued as MRI contrast agents in hope that they can be used at much lower doses that would minimize toxic-side effects of Gd^III release from traditional contrast agents. We construct here a new type of protein-based MRI contrast agent, a proteinaceous cage based on a stable insulin hexamer in which Gd^III is captured inside a water filled cavity. The macromolecular structure and the large number of "free" Gd^III coordination sites available for water binding lead to exceptionally high relaxivities per one Gd^III ion. The Gd^III slowly diffuses out of this cage, but this diffusion can be prevented by addition of ligands that bind to the hexamer. The ligands that trigger structural changes in the hexamer, SCN^- , Cl^- and phenols, modulate relaxivities through an outside-in signaling that is allosterically transduced through the protein cage. Contrast-o-phores based on protein-caged metal ions have potential to become clinical contrast agents with environmentally-sensitive properties.