An 8-Mercaptoquinoline Motif Enriches Minichromosome Maintenance Complex Components as Significant Metalloprotein Targets in Live Cells

Affinity-based probes are valuable tools for detecting binding interactions between small molecules and proteins in complex biological environments. Metalloproteins are a class of therapeutically significant biomolecules which bind metal ions as part of key structural or catalytic domains and are compelling targets for study. However, there is currently a limited range of chemical tools suitable for profiling the metalloproteome. Here, we describe the preparation and application of a novel, photoactivatable affinity based probe for detection of a subset of previously challenging to engage metalloproteins. The probe, bearing an 8 mercaptoquinoline metal chelator, was anticipated to engage several zinc metalloproteins, including the 26S proteasome subunit Rpn11. Upon translation of the labelling experiment to mammalian cell lysates, proteomic analysis revealed that several metalloproteins were competitively enriched. An 8-mercaptoquinoline diazirine probe was found to effectively enrich multiple components of the minichromosome maintenance complex, a zinc metalloprotein assembly with helicase activity essential to DNA replication.