Control of membrane dynamics by cooperative action of bacterial dynamin-like proteins and flotillins

• Applicant: Professor Dr. Marc Bramkamp
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2013 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 234082876

Proteins and lipids are heterogeneously distributed in biological membranes. Correct function of membrane proteins often depends on spatio-temporal organization into defined membrane areas. However, the lateral organization of the bacterial cell membrane has not been analyzed in detail and the influence on cellular processes such as cytokinesis and development remains largely unknown. We have already identified a bacterial flotillin that resides in membrane micro-domains and may contribute to lateral membrane organisation. Flotillins are raft marker proteins which are extensively modified on posttranslational level. These proteins assemble into oligomeric complexes which likely regulates their function. Using the anisotropic dye Laurdan, we have been able to show that bacterial flotillins directly influence membrane order, likely by preventing coalescence of liquid ordered regions. We will analyse how bacterial flotillin homologues in Bacillus subtilis are able to mediate spatial membrane organization and how this impacts function of membrane integral protein machineries such as the secretion system. In addition we have identified a bacterial dynamin-like protein, DynA that binds in a nucleotide-independent manner to negatively charged phospholipids. DynA is involved in membrane tethering and fusion. DynA localizes to septa and may contribute to efficient septum closure. DynA self-organizes into dynamic protein assemblies on membrane surfaces, thereby leading to membrane fusion. This process does not need GTP hydrolysis. Amazingly, we have evidence that DynA may be involved in phage resistance. Hence, similar to the related Mx proteins in vertebrates, bacterial dynamins could be part of a bacterial innate immune system against viral infection. We will study how DynA mediates membrane fusion by ordered complex formation and how this complex is disassembled after membrane fusion. Further we will clarify the cellular role of bacterial dynamins.

• DFG Programme: Research Grants