Supramolecular structure and enzyme catalysis: the groundplan of living cells

Abstract

Extracellular stimuli (e.g. light, hormones, pH, oxygen) trigger a coherent answer at the cellular level that leads the cell to different developmental paths, to stop division or to redirect metabolic fluxes. Chapter 2 argued that, at the cellular level, the passage from microscopic to macroscopic coherence could be given by instability of the dynamics of processes like polymerization-depolymerization of cytoskeleton components. One main piece of evidence that led us to suggest the autonomous dynamics of the cytoskeleton as an organizer of cellular activities was at the spatio-temporal ‘window’ of occurrence of polymerization-depolymerization processes that corresponded to the domain likely to give rise to macroscopic coherence at the cellular level, i.e. microtubules extend over several micrometres in a lapse of minutes (Kirschner and Mitchinson, 1986; Erickson and O’Brien, 1992). Instabilities in the autonomous dynamics of biological processes in a far from thermodynamic equilibrium domain give rise to self-organized behaviour. This behaviour could synchronize collective or systemic properties in cells such as metabolic fluxes (Cortassa et al.,1994a; Cortassa and Aon, 1994b). Redirection of metabolic fluxes as a mechanism of carbon and energy uncoupling has been shown to be associated to cell division and differentiation (sporulation) of Saccharomyces cerevisiae (Aon et al., 1995; Mónaco et al., 1995; Aon and Cortassa, unpublished).