SUPRAMOLECULAR ASSEMBLIES |
On the kinetics of adsorption and two-dimensional self-assembly of annexin A5 on supported lipid bilayers
Ralf P. Richter 1, Joséphine Lai Kee Him 2, Béatrice Tessier 2, Céline Tessier 2 and Alain R. Brisson 2*
1 University of Heidelberg
2 IECB
* To whom correspondence should be addressed. E-mail: a.brisson{at}iecb.u-bordeaux.fr.
Submitted on April 13, 2005
Revised on May 24, 2005
Accepted on 29 June 2005
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Abstract |
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Annexin A5 is a protein that binds to membranes containing negatively charged phospholipids in a calcium-dependent manner. We previously found that annexin A5 self-assembles into 2D crystals on supported lipid bilayers (SLBs) formed on mica while a monolayer of disordered trimers is formed on SLBs on silica (Richter and Brisson, Langmuir 2003, 19, 1632-1640). Here, we investigated in detail and correlated the adsorption kinetics of annexin A5 on SLBs, supported on silica and on mica, with the protein's 2D self-assembly behavior. For this study, quartz crystal microbalance with dissipation monitoring and ellipsometry were combined with atomic force microscopy. We find, in agreement with previous studies, that the adsorption behavior is strongly dependent on the concentration of dioleoylphosphatidylserine (DOPS) in the SLB and the calcium concentration in solution. The adsorption kinetics of annexin A5 are similar on silica-SLBs and on mica-SLBs, when taking into account the difference in accessible DOPS between silica-SLBs and mica-SLBs (Richter et al., Langmuir 2005, 21, 299-304). In contrast, 2D crystals of annexin A5 form readily on mica-SLBs, even at low protein coverage (
10%), while they are not found on silica-SLBs, except in a narrow range close to maximal coverage. These results enable to construct the phase diagram for the membrane binding and the states of 2D organization of annexin A5. The protein binds to the membrane in two different fractions, one reversible and the other irreversible, at a given calcium concentration. The adsorption is determined by the interaction of protein monomers with the membrane. We propose that the local membrane environment, as defined by the presence of DOPS, DOPC and calcium ions, controls the adsorption and reversibility of protein binding.
Key Words:
annexin A5, atomic force microscopy (AFM), mica, quartz crystal microbalance with dissipation monitoring (QCM D), silica, supported lipid bilayer (SLB)
