Intrinsic disorder of the bacterial cell division protein ZipA: Coil-to-brush conformational transition

The full-length ZipA protein from Escherichia coli, one of the essential elements of the cell division machinery, was studied in a surface model built as adsorbed monolayers. The interplay between lateral packing and molecular conformation was probed using a combined methodology based on the scaling analysis of the surface pressure isotherms and ellipsometry measurements of the monolayer thickness. The observed behavior is compatible with the one expected for an intrinsically disordered and highly flexible protein that is preferentially structured in a random coil conformation. At low grafting densities, ZipA coils organize in a mushroom-like regime, whereas a coil-to-brush transition occurs on increasing lateral packing. The structural results suggest a functional scenario in which ZipA acts as a flexible tether anchoring bacterial proto-ring elements to the membrane during the earlier stages of division.This work was partially financed under grants from the Ministerio de Economía y Competitividad of Spain (FIS2012-35723 and FIS2009-14650-C02-01 to F.M.; BIO2008-04478-C03 to M.Vi., G.R., and M.Ve.; BIO2011-28941-C03-01 to M.Vi.; BIO2011-28941-C03-02 to G.R.; and Consolider Ingenio en Nanociencia MolecularCSD2007-0010 to F.M. and M.V.); Comunidad de Madrid (CAM; S2005MAT-0283 and S2009MAT-1507 to F.M. and M.V., and S2006-BIO-0260 to M.Vi., G.R., and J.M.); the European Commission (DIVINOCELL FP7 HEALTH-F3-2009-223431 to M.Vi., G.R., and M.Ve.); and the Human Frontier Science Program (HFSP-RGP0050/2010 to M.Vi. and G.R.). I.L.-M. was partially supported by the Juan de la Cierva program (Ministerio de Economía y Competitividad) and the Research Consortium on Nanobiomaterials (NOBIMAT; CAM). P.L.-N. thanks Programa de Formación de Personal Investigador (FPI-CAM) for financial support.Peer Reviewe