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Updated: Apr 22, 2026

OaAEP1-Mediated Enzymatic Synthesis and Immobilization of Polymerized Protein for Single-Molecule Force Spectroscopy
Published on: February 5, 2020
Protein-polymer conjugation via ligand affinity and photoactivation of glutathione S-transferase
En-Wei Lin1, Natalie Boehnke, Heather D Maynard
1Department of Chemistry & Biochemistry and the California NanoSystems Institute, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095, United States.
Abstract:
A photoactivated, site-selective conjugation of poly(ethylene glycol) (PEG) to the glutathione (GSH) binding pocket of glutathione S-transferase (GST) is described. To achieve this, a GSH analogue (GSH-BP) was designed and chemically synthesized with three functionalities: (1) the binding affinity of GSH to GST, (2) a free thiol for polymer functionalization, and (3) a photoreactive benzophenone (BP) component. Different molecular weights (2 kDa, 5 kDa, and 20 kDa) of GSH-BP modified PEGs (GSBP-PEGs) were synthesized and showed conjugation efficiencies between 52% and 76% to GST. Diazirine (DA) PEG were also prepared but gave conjugation yields lower than for GSBP-PEGs. PEGs with different end-groups were also synthesized to validate the importance of each component in the end-group design. End-groups included glutathione (GS-PEG) and benzophenone (BP-PEG). Results showed that both GSH and BP were crucial for successful conjugation to GST. In addition, conjugations of 5 kDa GSBP-PEG to different proteins were investigated, including bovine serum albumin (BSA), lysozyme (Lyz), ubiquitin (Ubq), and GST-fused ubiquitin (GST-Ubq) to ensure specific binding to GST. By combining noncovalent and covalent interactions, we have developed a new phototriggered protein-polymer conjugation method that is generally applicable to GST-fusion proteins.
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