Nevertheless, YFP-MinDEc is partially able to alleviate the ΔminDBs phenotype, although it is not able to substitute fully for the role of B. subtilis MinD protein. The localization pattern of YFP-MinDEc was similar to previously observed GFP-MinDBs spiral localization (Barák et al., 2008). The cellular targeting of YFP-MinDEc was not influenced in ΔminDBs and in ΔdivIVAΔminDBs backgrounds, and this it appears to be independent of B. subtilis MinD and DivIVA proteins. Both MinDBs and MinDEc proteins have membrane-targeting sequences (MTS) with
amphipathic α-helices that play a crucial role in the attachment of the protein to the membrane (Szeto et al., 2002). MTS in both proteins are located at their C-terminus and differ in the length and amino acid composition. Despite these differences between the MTS, GFP-MinDEc most likely recognizes the same negatively charged
phospholipids in the screening assay membrane as GFP-MinDBs in B. subtilis (Barák et al., 2008). These findings could also explain the mechanism of MinDEc localization on helical trajectories in E. coli, although helical organization of negatively charged lipids in this microorganism has not been shown yet. The MinDEc N-terminus is believed to be essential for ATP binding, the central region for protein–protein interactions and the C-terminus for attachment to the membrane (Cordell & Löwe, 2001; Hayashi et al., 2001; Zhou & Lutkenhaus, 2004). We inspected three mutant GFP-MinDEc protein JNK inhibitor versions. The mutations I23N and S89P, located at the N-terminus, have no apparent influence on the function and localization of MinDEc in B. subtilis.
The last of the tested mutations, G209D, is predicted to be a part of a short strand and is probably exposed on the surface of the molecule (http://bioinf.cs.ucl.ac.uk/psipred/psiform.html). In this case the localization ability of the protein Ibrutinib purchase did not change, but the protein was not able any more to elongate B. subtilis cells when overexpressed. Although this mutation is not close to predicted ATP, MinC or MinE binding sites, the protein–protein interaction abilities may have been affected. The effect of the third component of the E. coli Min system, MinEEc on B. subtilis cells was tested. When overexpressed, MinEEc-GFP does not interfere with cell division. No significant cell length increase or formation of minicells was observed. In addition, MinEEc-GFP was spread throughout the cytoplasm in B. subtilis. It is known that in E. coli MinEEc localization to membrane is MinD dependent (Raskin & de Boer, 1997). Hence it is possible that MinDBs is not able to recruit MinEEc to the membrane. Nevertheless, further experiments are needed to determine whether MinEEc would form a ring and localize to the membrane in cells expressing both MinEEc and MinDEc and if these proteins would behave as dynamically in B. subtilis as in E. coli.