Biology subjects

Mais, C.-N.

Publications and source records attributed to Mais, C.-N..

3 recordsLinked to original sources

bioRxiv2025

Molecular basis of ParA ATPase activation by the CTPase ParB during bacterial chromosome segregation

DNA segregation by bacterial ParABS systems is mediated by transient tethering interactions between nucleoid-bound dimers of the ATPase ParA and centromere (parS)-associated complexes of the clamp-forming CTPase ParB. The lifetime of these interactions is limited by the ParB-dependent activation of ParA ATPase activity. Here, we elucidate the functional interplay between ParA and ParB in the model bacterium Myxococcus xanthus. We demonstrate that the N-terminal ParA-binding motif of ParB associates with a conserved bipartite binding pocket at the ParA dimer interface, in a manner dependent on ParB clamp closure. Moreover, we show that ParB and non-specific DNA interact cooperatively with ParA and synergistically induce structural changes at its Walker A and Walker B motifs that correlate with the activation of ParA ATPase activity. These results advance our understanding of the mechanism underlying DNA transport by the ParABS system and may help to unravel the mode of action of related cargo-positioning systems.

microbiology↗

bioRxiv2024

Frequent transitions in self-assembly across the evolution of a central metabolic enzyme

Many enzymes assemble into homomeric protein complexes comprising multiple copies of one protein. Because structural form is usually assumed to follow function in biochemistry, these assemblies are thought to evolve because they provide some functional advantage. In many cases, however, no specific advantage is known and, in some cases, quaternary structure varies among orthologs. This has led to the proposition that self-assembly may instead vary neutrally within protein families. The extent of such variation has been difficult to ascertain because quaternary structure has until recently been difficult to measure on large scales. Here, we employ mass photometry, phylogenetics, and structural biology to interrogate the evolution of homo-oligomeric assembly across the entire phylogeny of prokaryotic citrate synthases - an enzyme with a highly conserved function. We discover a menagerie of different assembly types that come and go over the course of evolution, including cases of parallel evolution and reversions from complex to simple assemblies. Functional experiments in vitro and in vivo indicate that evolutionary transitions between different assemblies do not strongly influence enzyme catalysis. Our work suggests that enzymes can wander relatively freely through a large space of possible assemblies and demonstrates the power of characterizing structure-function relationships across entire phylogenies.

evolutionary biology↗

bioRxiv2024

Polar confinement of a macromolecular machine by an SRP-type GTPase

The SRP-type GTPase FlhF, along with its regulator FlhG, orchestrates the localization and quantity of flagella in bacteria. Our study reveals that FlhF anchors developing flagellar structures to the polar landmark protein HubP/FimV, thereby restricting their formation to the cell pole. Specifically, the GTPase domain of FlhF interacts with HubP, while an as-yet-uncharacterized structured domain at the N-terminus of FlhF binds to FliG. This FlhF-bound FliG subsequently engages with the MS-ring protein FliF, but not with the C-ring proteins FliM/FliN. Consequently, FlhFs interaction with HubP/FliG recruits a functional FliF/FliG complex to the pole, while FlhGs modulation of FlhF controls FliGs interaction with FliM/FliN, thereby regulating the progression of flagellar assembly at the pole. Significance statementFlagella serve as bacterial locomotion organelles, with their number and location, known as the flagellation pattern, being species-specific and among the earliest taxonomic criteria in microbiology. Bacteria replicate their flagellation pattern with each cell division. Flagella localization and abundance depends on the SRP-type GTPase FlhF, together with its regulator FlhG. Our study clarifies the mechanism through which FlhF coordinates the polar positioning of the flagellum, working in tandem with the polar landmark protein HubP and aiding in the assembly of flagellar MS-ring/C-ring components at the cellular pole.

microbiology↗