ATPase activity measurement of DNA replicative helicase from Bacillus stearothermophilus by malachite green method

Identification of drug-like molecules targeting the ATPase activity of dynamin-like EHD4

Eps15 (epidermal growth factor receptor pathway substrate 15) homology domain-containing proteins (EHDs) comprise a family of eukaryotic dynamin-related ATPases that participate in various endocytic membrane trafficking pathways. Dysregulation of EHDs function has been implicated in various diseases, including cancer. The lack of small molecule inhibitors which acutely target individual EHD members has hampered progress in dissecting their detailed cellular membrane trafficking pathways and their function during disease. Here, we established a Malachite green-based assay compatible with high throughput screening to monitor the liposome-stimulated ATPase of EHD4. In this way, we identified a drug-like molecule that inhibited EHD4's liposome-stimulated ATPase activity. Structure activity relationship (SAR) studies indicated sites of preferred substitutions for more potent inhibitor synthesis. Moreover, the assay optimization in this work can be applied to other dynamin family members showing a weak and liposome-dependent nucleotide hydrolysis activity.

Diverse Mechanisms of Helicase Loading during DNA Replication Initiation in Bacteria

Initiation of DNA replication is required for cell viability and passage of genetic information to the next generation. Studies in Escherichia coli and Bacillus subtilis have established ATPases associated with diverse cellular activities (AAA+) as essential proteins required for loading of the replicative helicase at replication origins. AAA+ ATPases DnaC in E. coli and DnaI in B. subtilis have long been considered the paradigm for helicase loading during replication in bacteria. Recently, it has become increasingly clear that most bacteria lack DnaC/DnaI homologs. Instead, most bacteria express a protein homologous to the newly described DciA (dnaC/dnaI antecedent) protein. DciA is not an ATPase, and yet it serves as a helicase operator, providing a function analogous to that of DnaC and DnaI across diverse bacterial species. The recent discovery of DciA and of other alternative mechanisms of helicase loading in bacteria has changed our understanding of DNA replication initiation. In this review, we highlight recent discoveries, detailing what is currently known about the replicative helicase loading process across bacterial species, and we discuss the critical questions that remain to be investigated.