Biophysical Regulation of Lipid Biosynthesis in the Plasma Membrane

¹ Imperial College London
² Imperial College

^* To whom correspondence should be addressed. E-mail: m.barahona{at}imperial.ac.uk.

Submitted on July 27, 2007
Revised on September 7, 2007
Accepted on 11 October 2007

	Abstract

We present a cellular model of lipid biosynthesis in the plasma membrane that couples biochemical and biophysical features of the enzymatic network of the cell-wall-less Mycoplasma Acholeplasma laidlawii. In particular, we formulate how the stored elastic energy of the lipid bilayer can modify the activity of curvature-sensitive enzymes through the binding of amphipathic -helices. As the binding depends on lipid composition, this results in a biophysical feedback mechanism for the regulation of the stored elastic energy. The model shows that the presence of feedback increases the robustness of the steady state of the system, in the sense that biologically inviable non-bilayer states are less likely. We also show that the biophysical and biochemical features of the network have implications as to which enzymes are most efficient at implementing the regulation. The network imposes restrictions on the steady-state balance between bilayer and non-bilayer lipids and on the concentrations of particular lipids. Finally, we consider the influence of the length of the amphipathic -helix on the efficacy of the feedback and propose experimental measurements and extensions of the modelling framework.

Key Words: NON-BILAYER LIPIDS, ROBUST NETWORKS, SPONTANEOUS CURVATURE, STORED CURVATURE ELASTIC ENERGY