CRISPR-based oligo recombineering prioritizes apicomplexan cysteines for drug discovery

Nucleophilic amino acids are important in covalent drug development yet underutilized as anti-microbial targets. Chemoproteomic technologies have been developed to mine chemically accessible residues via their intrinsic reactivity towards electrophilic probes but cannot discern which chemically reactive sites contribute to protein function and should therefore be prioritized for drug discovery. To address this, we have developed a CRISPR-based oligo recombineering (CORe) platform to support the rapid identification, functional prioritization and rational targeting of chemically reactive sites in haploid systems. Our approach couples protein sequence and function with biological fitness of live cells. Here we profile the electrophile sensitivity of proteinogenic cysteines in the eukaryotic pathogen Toxoplasma gondii and prioritize functional sites using CORe. Electrophile-sensitive cysteines decorating the ribosome were found to be critical for parasite growth, with target-based screening identifying a parasite-selective anti-malarial lead molecule and validating the apicomplexan translation machinery as a target for ongoing covalent ligand development.

Use of computerized multidimensional scaling to compare immunoelectron microscopy data with protein near-neighbor information: application to the 30S ribosome from Escherichia coli

A three-dimensional model of the protein arrangement in the Escherichia coli 30S ribosome was constructed by using computerized multidimensional scaling of immunoelectron microscope data. This enabled data comparison between the new electron microscope technique and other methods such as crosslinking, chemical protection, affinity labeling, energy transfer, and assembly interactions. The immunoelectron microscopy data are reasonably consistent with those from other sources. Reasons for some inconsistent data are discussed and our calculation of the dimensions of the proteins, both globular and elongated, are summarized.