Uncommon activation of SynDLP, the fusogenic Dynamin-like protein of the cyanobacterium Synechocystis sp. PCC 6803

Abstract Dynamin-like proteins are membrane remodeling GTPases with well-understood functions in eukaryotic cells. However, bacterial Dynamin-like proteins are still poorly investigated. SynDLP, the Dynamin-like protein of the cyanobacterium Synechocystis sp. PCC 6803, forms ordered oligomers in solution. The 3.7 Å resolution cryo-EM structure of SynDLP oligomers reveals the presence of oligomeric stalk interfaces typical for eukaryotic Dynamin-like proteins. The bundle signaling element domain shows distinct features, such as an intramolecular disulfide bridge that affects the GTPase activity, or an expanded intermolecular interface with the GTPase domain. Such atypical GTPase domain interfaces might be a GTPase activity regulating tool in oligomerized SynDLP. Furthermore, we show that SynDLP interacts with and intercalates into membranes containing negatively charged thylakoid membrane lipids. SynDLP is able to fuse membranes in a nucleotide-independent process in vitro. Thus, we assign SynDLP to the subclass of fusogenic Dynamin-like proteins.