Synergistic stabilization of a double mutant in chymotrypsin inhibitor 2 from a library screen in <i>E. coli</i>

Most single point mutations destabilize folded proteins. Mutations that stabilize a protein typically only have a small effect and multiple mutations are often needed to substantially increase the stability. Multiple point mutations may act synergistically on the stability, and it is often not straightforward to predict their combined effect from the individual contributions. Here, we have applied an efficient in-cell assay in E. coli to select variants of the barley chymotrypsin inhibitor 2 with increased stability. We find two variants that are more than 3.8 kJ mol(−1) more stable than the wild-type. In one case, the increased stability is the effect of the single substitution D55G. The other case is a double mutant, L49I/I57V, which is 5.1 kJ mol(−1) more stable than the sum of the effects of the individual mutations. In addition to demonstrating the strength of our selection system for finding stabilizing mutations, our work also demonstrate how subtle conformational effects may modulate stability

Exploring the NCS-382 Scaffold for CaMKIIα Modulation: Synthesis, Pharmacology, and Biophysical Characterization of Ph-HTBA as a Novel High-Affinity Brain-Penetrant Stabilizer of the CaMKIIα Hub Domain

Ca2+/calmodulin-dependent protein kinase II alpha (CaMKIIα) is a brain-relevant kinase and an emerging drug target for ischemic stroke and neurodegenerative disorders. Despite various reported CaMKIIα inhibitors, their usefulness is limited by low subtype selectivity and brain permeability. (E)-2-(5-Hydroxy-5,7,8,9-tetrahydro-6H-benzo[7]annulen-6-ylidene)acetic acid (NCS-382) is structurally related to the proposed neuromodulator, γ-hydroxybutyric acid, and is a brain-penetrating high nanomolar-affinity ligand selective for the CaMKIIα hub domain. Herein, guided by in silico approaches, we synthesized the first series of NCS-382 analogs displaying improved affinity and preserved brain permeability. Specifically, we present Ph-HTBA (1i) with enhanced mid-nanomolar affinity for the CaMKIIα binding site and a marked hub thermal stabilization effect along with a distinct CaMKIIα Trp403 flip upon binding. Moreover, Ph-HTBA has good cellular permeability and low microsomal clearance and shows brain permeability after systemic administration to mice, signified by a high Kp,uu value (0.85). Altogether, our study highlights Ph-HTBA as a promising candidate for CaMKIIα-associated pharmacological interventions and future clinical development

A dual-reporter system for investigating and optimizing protein translation and folding in E. coli

Heterologous expression of recombinant proteins often results in misfolding, aggregation and degradation. Here, we show an in vivo dual-biosensor system that simultaneously assesses protein translation and protein folding, thereby enabling rapid screening of expression strains as well as mutant libraries

Ca2+-free Calmodulin mutant N53I

Assembly members: entity_1, polymer, 148 residues, 16720.404 Da. Natural source: Common Name: Human Taxonomy ID: 9606 Superkingdom: Eukaryota Kingdom: Metazoa Genus/species: Homo sapiens Experimental source: Production method: recombinant technology Host organism: Escherichia coli BL21(DE3) Entity Sequences (FASTA): entity_1: ADQLTEEQIAEFKEAFSLFD KDGDGTITTKELGTVMRSLG QNPTEAELQDMIIEVDADGN GTIDFPEFLTMMARKMKDTD SEEEIREAFRVFDKDGNGYI SAAELRHVMTNLGEKLTDEE VDEMIREADIDGDGQVNYEE FVQMMTA