title: Characterization of a bacterial self-assembly surface layer protein and its application as an electrical nanobiosensor.
abstract: Bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (Archaea and bacteria), which can self-assemble into two-dimensional (2D) crystalline arrays. Production and characterization of the bacterial S-layer protein (SLP) from Geobacillus stearothermophilus, a thermophilic bacterium, are demonstrated in this study. Based on this, purified SLPs were applied for wrapping around single-walled carbon nanotubes (CNTs) and applying as electrochemical sensing tools. For the large scale production of SLP, fed-batch culture of G. stearothermophilus was carried out by DO-stat strategy. Purified SLPs were characterized by atomic force microscopy (AFM). After recrystallization of purified SLPs with gold colloids, the formation of two-dimensional (2D) oblique lattice was observed by transmission electron microscopy (TEM). Metallic or near metallic characteristics of CNTs were measured by current-voltage (I-V) analyzer. By high-cell density cultivation, cells grew to 10 g/l of dry cell weight in 65 h and the S-layer contents were achieved up to 40% of total proteins. The SLPs were purified to electrophoretic homogeneity and the molecular mass was estimated to be about 105 kDa. The purified SLPs were self-assembled and confirmed their hexagonal symmetry lattice structure. The SLP subunits were cross-linked to each other and to the underlying CNTs by non-covalent interaction, which was caused to change the electric current between natural CNTs and SLP-wrapped CNTs. One-dimensional structure and large aspect ratio of the functionalized CNTs may allow effective targeting of biomolecules by specific binding, such as protein-protein, DNA-DNA, and protein-ligand interaction. Bacterial SLP could be used as a biological template for immobilization molecular array, and provides new approaches for nanoelectronic biosensor applications.
authors: BioProcess Engineering Research Center, Institute for the BioCentury, KAIST 335 Gwahangno, Yuseong-gu, Daejeon 305-701, Korea.
authors: Tae Jung
authors: TJ
authors: Park
authors: Seek Jae
authors: SJ
authors: Lee
authors: Jong Pil
authors: JP
authors: Park
authors: Min Ho
authors: MH
authors: Yang
authors: Jong Hyun
authors: JH
authors: Choi
authors: Sang Yup
authors: SY
authors: Lee
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D002244:Carbon / Q000378:metabolism; D002452:Cell Count; D003460:Crystallization; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D055664:Electrochemical Techniques / Q000379:methods; D001411:Geobacillus stearothermophilus / Q000737:chemistry / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D018625:Microscopy, Atomic Force; D008970:Molecular Weight; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009584:Nitrogen / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D008562:Membrane Glycoproteins; D037742:Nanotubes, Carbon; C055764:S-layer proteins; D002244:Carbon; D009584:Nitrogen