Members of the Dynamin family are of broad cellular importance with roles in endocytosis, plastid biogenesis, animal and plant cytokinesis, viral resistance and many others. They are large multi-domain proteins that minimally comprise an N-terminal GTPase domain, a ‘bundle-signalling element’ or neck domain, and a stalk/trunk domain. Classical dynamins are supplemented with a pleckstrin homology (PH) domain for lipid binding specificity and a C-terminal proline-rich domain for multiple protein-protein interactions and functional tuning.
Although membrane fission and fusion are opposing processes, both appear dependent on basic dynamin-like properties such as lipid binding and polymerization, in which membrane is forced, under extreme curvature, to form a highly unstable tubular conformation. Dynamin nucleotide hydrolysis and conformational change within the polymer is then somehow coupled to membrane fission or fusion through still poorly understood mechanisms.
Dynamin family members are mechano-chemical enzymes capable of undergoing radical conformational change. For example, the bacterial dynamin-like protein (BDLP) from the cyanobacteria Nostoc punctiforme undergoes substantial structural rearrangment triggered by nucleotide and membrane binding (see movie on right).
Previously, we discovered that dynamin is not exclusive to the Eukaryota but is actually well radiated in the Eubacteria. Working on BDLP, we used a fusion of X-ray crystallography and cryo electron microscopy to build a molecular model of an entire BDLP-lipid tube, which showed in unprecedented detail how a dynamin family member can induce lipid curvature. The function of BDLP in cyanobacteria, and dynamins in general in bacteria is still currently unclear.