Membrane reconstitution of FtsZ-ZipA complex inside giant spherical vesicles made of E. coli lipids: Large membrane dilation and analysis of membrane plasticity

During the division process of Escherichia coli, the globular protein FtsZ is early recruited at the constriction site. The Z-ring, based on FtsZ filaments associated to the inner cell membrane, has been postulated to exert constriction forces. Membrane anchoring is mediated by ZipA, an essential transmembrane protein able to specifically bind FtsZ. In this work, an artificial complex of FtsZ–ZipA has been reconstituted at the inner side of spherical giant unilamellar vesicles made of E. coli lipids. Under these conditions, FtsZ polymerization, triggered when a caged GTP analogue is UV-irradiated, was followed by up to 40% vesicle inflation. The homogeneous membrane dilation was accompanied by the visualization of discrete FtsZ assemblies at the membrane. Complementary rheological data revealed enhanced elasticity under lateral dilation. This explains why vesicles can undergo large dilations in the regime of mechanical stability. A mechanical role for FtsZ polymers as promoters of membrane softening and plasticization is hypothesized.This work was partially financed by MICINN (grants FIS2009-14650-C02-01 and FIS2012-35723 to FM and Consolider Ingenio en Nanociencia MolecularCSD 2007-0010 to FM and MVe) and CAM (grants S2005MAT-0283 and S2009MAT-1507 to FM and MVe). This work was also supported by grants from Plan Nacional (Ministerio de Ciencia e Innovación, Spain)BIO2008-04478-C03, DIVINOCELL FP/HEALTH-F3-2009-223432 (European Commision) to MVi and MVe, and COMBACT S-BIO-0260/2006 (Comunidad de Madrid) to MVi and JM. I L-M was supported by Juan de la Cierva program (MICINN). JM was recipient of a Ramón y Cajal fellowship financed by the European Social Fund and MICINN. PL-N was a pre-doctoral fellow from the Comunidad de Madrid, Spain.Peer Reviewe