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. The members of this family use GTP hydrolysis to cause membrane curvature and constriction. The recent discovery of bacterial dynamin-like proteins (BDLPs) that bind and remodel membranes has brought to light the conserved role these proteins play in regulating membrane dynamics across the domains of life. We have identified a family of BDLPs in a number of enteric bacterial pathogens, in particular the gastric pathogen Helicobacter pylori. This family of proteins is most closely related to proteins from enterotoxigenic Escherichia coli that have been implicated in bacterial membrane vesicle formation and toxin delivery.

Most BDLP genes are found as a pair, each one encoding a full-length dynamin homolog. In H. pylori, one of these genes is split into two (dfmC and dfmB), with a predicted membrane-spanning helix adjacent to the split—at the N-terminus of DfmB. The gene arrangement and presence of a predicted transmembrane helix implies that these proteins may act as a hetero-complex involved in membrane remodeling. Our hypothesis is that DfmCBA are part of membrane vesicle production or a secretory pathway important for pathogenesis. We are performing protein-protein interaction studies of DfmCBA using the bacterial two-hybrid system, and we are determining the subcellular localization by biochemical fractionation combined with mass spectrometry, and microscopy studies. These studies have so far indicated that DfmB is a membrane protein, whereas DfmA and DfmC are found in the soluble fraction. Using genome editing techniques available for H. pylori, we are carrying out deletion studies to investigate the role of DfmCBA and the membrane domain of DfmB in H. pylori growth, membrane dynamics and pathogenesis.