Membrane dynamics are essential for a number of important cellular processes. In eukaryotic cells, membrane fusion and fission are often controlled by large GTPases of the dynamin protein superfamily. These proteins use GTP hydrolysis to promote membrane curvature and constriction. The recent discovery of bacterial dynamin-like proteins (BDLPs) that bind and remodel membranes in vitro, has suggested that these proteins may regulate membrane dynamics across the domains of life. BDLPs have been identified in many bacteria, including the human gastric pathogen Helicobacter pylori. H. pylori BDLPs are most closely related to proteins from enterotoxigenic Escherichia coli that have previously been implicated in bacterial membrane vesicle formation and toxin delivery to the host (Michie et al, 2014).
BDLP genes are typically found as a pair, each one encoding a full-length dynamin homolog. However, in most strains of H. pylori, one of these is split into two separate ORFs (dfmC and dfmB). We found that dfmC and dfmB are co-transcribed, whereas the downstream dfmA gene is expressed in a separate transcript. Interestingly, in isolated clones of H. pylori 26695, we have identified a single-nucleotide insertion that results in a joined (full-length) dynamin homolog (dfmCB); the consequences of this genotype variation are currently under investigation. Nevertheless, the clustered gene arrangement and presence of a predicted transmembrane helix in dfmB suggests that these proteins might act as a hetero-complex involved in membrane remodeling, e.g. for membrane vesicle production important for pathogenesis. We are using gene knock-out studies combined with protein localization and interaction studies to understand the function of these genes in H. pylori.