Structurally characterising biomolecular recognition at the solid-liquid interface: an example using immunoglobulin G bound to membrane protein arrays on gold

Le Brun, AP; Holt, SA; Lakey, JH; Shah, D; Majkrzak, CF

Structurally characterising biomolecular recognition at the solid-liquid interface: an example using immunoglobulin G bound to membrane protein arrays on gold

Date

2010-06-29

Authors

Publisher

Neutron Scattering Society of America

Abstract

Proteins can be immobilised on surfaces to make arrays with potential uses in tissue engineering, proteomics and point of use diagnostic devices. Outer membrane proteins (OMP) from Escherichia coli have a beta-barrel structure, making ideal protein engineering scaffolds for building arrays. The proteins can be immobilised onto flat gold surfaces by introducing a cysteine residue into their periplasmic turns. The thiol group of the cysteine will form a strong gold-thiolate bond immobilising the OMP to the surface in a specific and correct orientation. The membrane layer is completed by the immobilisatin of a lipid with a thiol head group to the gold surface. Here we use the transmembrane section of the monomeric protein OmpA (TmOmpA). The Z domain of Staphylococcus aureau protein A has been engineered into the N - terminal of a circularly permuted TmOmpA to create the protein ZZctOmpA. The Z domain can bind immunoglobulin G (IgG) at its constant region leaving the variable regions free to bind antigen. The structure of this model protein array was probed using magnetic contrast neutron reflection (MCNR). MCNR uses polarised neutrons which reflect differently from a magnetic metal layer according to their two spin states (spin up and spin down). The magnetic layer deposited under the gold surface and provides additional scattering length density contrast to very complex layer systems without needing to make any changes to the biological layer. The collection of two complimentary but independent data sets allows for more accurate modelling of the resulting high resolution data. The data presented will show the assembly steps for creating the array detailing the surfaces used, the ZZctOmpA and lipid components as well as information on the orientation of bound antibody and antigen.

Keywords

Gold, Membrane proteins, Immunoglobulins, Cysteine, Lipids, Neutron reflectors

Citation

Le Brun, A., Holt, S., Lakey, J., Shah, D., & Majkrzak, C. (2010). Structurally characterising biomolecular recognition at the solid-liquid interface: an example using immunoglobulin G bound to membrane protein arrays on gold. Presentation to the 5th American Conference on Neutron Scattering 2010 (ACNS2010), 26th - 30th June 2010, Ottawa, Ontaro, Canada: Fairmont Château Laurier.