Applied and Environmental Microbiology, September 1999, p. 4134-4140, Vol. 65, No. 9
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Biotechnology,
Received 24 March 1999/Accepted 7 July 1999
An expression system designed for cell surface display of hybrid
proteins on Staphylococcus carnosus has been evaluated for the display of Staphylococcus aureus protein A (SpA)
domains, normally binding to immunoglobulin G (IgG) Fc but here
engineered by combinatorial protein chemistry to yield SpA domains,
denoted affibodies, with new binding specificities. Such affibodies,
with human IgA or IgE binding activity, have previously been selected from a phage library, based on an SpA domain. In this study, these affibodies have been genetically introduced in monomeric or dimeric forms into chimeric proteins expressed on the surface of S. carnosus by using translocation signals from a
Staphylococcus hyicus lipase construct together with
surface-anchoring regions of SpA. The recombinant surface proteins,
containing the IgA- or IgE-specific affibodies, were demonstrated to be
expressed as full-length proteins, localized and properly exposed at
the cell surface of S. carnosus. Furthermore, these
chimeric receptors were found to be functional, since recombinant
S. carnosus cells were shown to have gained IgA and IgE
binding capacity, respectively. In addition, a positive effect in terms
of IgA and IgE reactivity was observed when dimeric versions of the
affibodies were present. Potential applications for recombinant
bacteria with redirected binding specificity in their surface proteins
are discussed.
*
Corresponding author. Mailing address: Department of
Biotechnology, Royal Institute of Technology (KTH), S-100 44 Stockholm, Sweden. Phone: 46 8 790 6497. Fax: 46 8 245452. E-mail:
stefans{at}biochem.kth.se.
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