PERIPHERAL PROTEIN ADSORPTION TO LIPID-WATER INTERFACES: THE FREE AREA THEORY

¹ MOUNT SINAI SCHOOL OF MEDICINE
² Hormel Inst., U of MN

^* To whom correspondence should be addressed. E-mail: hlbroc{at}hi.umn.edu.

Submitted on March 8, 2005
Revised on April 10, 2005
Accepted on 15 August 2005

	Abstract

In fluid monolayers approaching collapse, phospholipids and their complexes with diacylglycerols, hinder adsorption to the monolayer of the amphipathic protein, colipase. Herein, a statistical, free-area model, analogous to that used to analyze two-dimensional lipid diffusion, is developed to describe regulation by lipids of the initial rate of protein adsorption from the bulk aqueous phase to the lipid-water interface. It is successfully applied to rate data for colipase adsorption to phospholipid alone and yields realistic values of the two model parameters; the phospholipid excluded area and the critical free surface area required to initiate adsorption. The model is further developed and applied to analyze colipase adsorption rates to mixed monolayers of phospholipid and phospholipid-diacylglycerol complexes. The results are consistent with complexes being stably associated over the physiologically-relevant range of lipid packing densities and being randomly-distributed with uncomplexed phospholipid molecules. Thus, complexes should form in fluid regions of cellular membranes at sites of diacylglycerol generation. If so, by analogy with the behavior of colipase, increasing diacylglycerol may not trigger translocation of some amphipathic peripheral proteins until its abundance locally exceeds its mole fraction in complexes with membrane phospholipids.

Key Words: colipase, diacylglycerol, excluded area, kinetic model, lipid monolayer, phospholipid

This article has been cited by other articles:

				A. A. Sethi, J. A. Stonik, F. Thomas, S. J. Demosky, M. Amar, E. Neufeld, H. B. Brewer, W. S. Davidson, W. D'Souza, D. Sviridov, et al. Asymmetry in the Lipid Affinity of Bihelical Amphipathic Peptides: A STRUCTURAL DETERMINANT FOR THE SPECIFICITY OF ABCA1-DEPENDENT CHOLESTEROL EFFLUX BY PEPTIDES J. Biol. Chem., November 21, 2008; 283(47): 32273 - 32282. [Abstract] [Full Text] [PDF]

				F. Miano, X. Zhao, J. R. Lu, and J. Penfold Coadsorption of Human Milk Lactoferrin into the Dipalmitoylglycerolphosphatidylcholine Phospholipid Monolayer Spread at the Air/Water Interface Biophys. J., February 15, 2007; 92(4): 1254 - 1262. [Abstract] [Full Text] [PDF]