Genetically Engineered S-Layer Proteins, S-Layer-Specific Heteropolysaccharides and S-Layer-Associated Exoenzymes as Versatile Building Blocks in Nanobiotechnology

Christina Altmutter1, Judith Ferner-Ortner1, Magdalena Pleschberger1, Dietmar Pum1, Rajesh R. Naik2, Uwe B. Sleytr1, and Margit Sára1

1Center for NanoBiotechnology and University of Natural Resources and Applied Life Sciences, Gregor Mendel St. 33, A-1180 Wien, Austria, and
2Air Force Research Laboratory, Materials and Manufacturing Directorate




Crystalline bacterial surface layer (s-layer) proteins have the intrinsic tendency to self-assemble into two-dimensional arrays in suspension and on solid supports. Currently, the molecular construction kit is being further developed for designing fusion proteins that comprise the N-terminal secondary cell wall polymer (SCWP)-binding domain, the self-assembly domain and a fused functional sequence. The N-terminal part of the S-layer protein SbpA of Bacillus sphaericus CCM 2177 carries three S-layer homologous motifs (SLH) which are involved in anchoring the S-layer subunits to the rigid cell wall layer via the pyruvylated SCWP, which is exploited as biomimetic linker to artificial supports. Recently, the putative enzyme required for pyruvylation of SCWP has been identified and shall exploited for the production of of substitutes for SCWPs. The cell-associated high-molecular-mass exoamylase of Geobacillus stearothermophilus ATCC 12980 binds to the S-layer protein SbsC as well as to the SCWP. The aim is to identify the smallest sequence recognizing the SCWP which could be exploited as a universal anchor for S-layer fusion proteins. S-layer fusion proteins incorporating metal binding peptide sequences for silver or cobalt shall be used as patterning elements for the bottom-up fabrication of regularly arranged nanoparticles or carbon nanotubes.