9P4E

Crystal Structure of Engineered glutamine binding protein and a Gd-DOTA ligand - no GLN bound

This is a non-PDB format compatible entry.

Summary for 9P4E

• Entry DOI: 10.2210/pdb9p4e/pdb
• Related: 9p4d
• Descriptor: Amino acid ABC transporter substrate-binding protein, SULFATE ION, ACETATE ION, ... (8 entities in total)
• Functional Keywords: amino acid abc transporter, substrate binding protein, metal binding protein
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 26922.30

Authors

Bruchs, A.T.,Wilson, C.A.,Boggs, D.G.,Fatima, S.,Bridwell-Rabb, J.,Olshansky, L. (deposition date: 2025-06-16, release date: 2026-01-14)

Primary citation

Wilson, C.A.,Bruchs, A.T.,Fatima, S.,Boggs, D.G.,Bridwell-Rabb, J.,Olshansky, L.
Development of a glutamine-responsive MRI contrast agent.
Chem Sci, 2025

PubMed Abstract: Magnetic resonance imaging (MRI) is widely used to visualize disease, and image quality can be improved through use of MRI contrast agents. Currently available agents produce a signal based solely on spatial distribution, but modern metabolic profiling has uncovered a variety of biomarkers for disease. For example, tumors greatly increase their uptake and catabolism of glutamine (Gln), leading to modified local concentration. Our laboratory previously developed a switchable artificial metalloprotein (swArM) platform in which Gln-binding causes a protein conformational change that modifies the physicochemical environment of an installed metallocofactor. Installing MRI-active metallocofactors within swArMs, we present a proof-of-concept approch toward the development of an analyte-responsive MRI contrast agent. To develop these swArMs, we tested several MRI-active metals (Gd, Dy), chelating ligands (DOTA, DTPA, NOTA), and attachment sites, as well as the impacts of peripheral mutations on the Gln-responsive signal. In each case, metal content was analytically defined, and Gln-binding affinity was determined by isothermal titration calorimetry. Circular dichroism was used to verify that our swArMs could still undergo the conformational change. X-ray diffraction structures of the and swArMs further revealed that the metallocofactor is significantly solvent-exposed in both conformations, but exhibits additional interactions with the protein in the state coinciding with the observed increase in relaxivity of ∼60% upon Gln-binding.

PubMed: 41395538
DOI: 10.1039/d5sc05987a

Experimental method

X-RAY DIFFRACTION (2.02 Å)