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1Post Graduate & Research Department of Microbiology, K.S.Rangasamy College of Arts and Science (Autonomous), Tiruchengode – 637 215. 2Centre for Nano Science and Technology, K.S.Rangasamy College of Technology (Autonomous), Tiruchengode – 637 215. (E-mail: aravindhbiotech@gmail.com)

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Scanning Electron Microscope image of Bacillaceae

To guarantee that the S-layer subunits attach in uniform orientation, which is extremely important if S-layer fusion proteins are used for building up functional monomolecular protein lattices, SCWP have been exploited as biomimetic linkers for pre-coating solid supports.

Transmission Electron Microscope image of Bacillaceae

One of the most remarkable features of many prokaryotic organisms (archaea and bacteria) is the presence of a regularly ordered surface layer (S layer) as the outermost component of the cell envelope. Slayers can act as (a) a framework to determine and maintain cell shape and cell division in archaea that possess S-layers as exclusive wall component; (b) protective coats, molecular sieves, as well as molecule and ion traps; (c) structures involved in cell adhesion and surface recognition; (d) templates for fine grain mineralization; (e) adhesion sites for cell-associated exoenzymes, and (f) virulence factors in pathogenic organisms with an important role in invasion and survival within the host.

Schematic drawing showing (i) that S-layer proteins from Bacillaceae are bound to the peptidoglycan-containing layer via the secondary cell-wall polymer (SCWP); (ii) the structural organization of S-layer proteins consisting of the N-terminal cell-wall-anchoring domain and the self- assembly domain; (iii) the formation of selfassembly products in suspension; (iv) the recrystallization of isolated S-layer subunits on supports optionally pre-coated with SCWP. On supports not precoated with SCWP, the S-layer subunits may either attach with their inner or outer surface. Biological materials can serve as nanotemplates for ‘bottom-up’ fabrication. In fact, this is considered one of the most promising ‘bottom-up’ approaches, mainly due to the nearly infinite types of templates available. Organism

S-layers

The self-assembly process is strongly dependent on the presence of bivalent cations, such as calcium ions. Slayer proteins self-assemble in suspension and recrystallize on various types of solid supports, as well as on lipid layers and liposomes. However, depending on the physicochemical properties of the underlying support, the S-layer subunits attach either with the outer or via the inner surface, so that the complementary surface remains exposed to the ambient environment. During the last few years, S-layer technology has advanced by the construction of S-layer fusion proteins that comprise (a) an accessible N-terminal SCWP- binding domain, which can be exploited for oriented binding and recrystallization on artificial supports pre- coated with SCWP, (b) the selfassembly domain, and (c) a C-terminally fused functional sequence.

Symmetry Schematic representation of types of S-layer lattice grouped according to possible 2D space group symmetries.

Lactobacillus Buchneri 41021/251

Desulfotomaculum nigrificans NCIB8706

Schematic drawing of (A) the cell envelope of a Gram-positive S-layer carrying organism. (B) Exploitation of the thiolated secondary cell-wall polymer (SCWP) as biomimetic linker to a gold chip for an oriented binding of S-layer fusion proteins. In S-layer fusion proteins, the C-terminal part is replaced by the fused foreign functional sequence or domain.

Morphological units were chosen arbitrarily and are shown in dark gray.

Thermoanaerobacter thermohydrosulfuricus L111-69

Electron micrographs of freeze-etched preparations of intact bacteria. Chemical analyses and genetic studies revealed that the monomolecular Slayer is the result of the secretion and subsequent crystallization of a single homogeneous protein or glycoprotein species with a molecular mass ranging from 40 to 200 kDa. (A) Schematic illustration of recrystallization of isolated S-layer subunits into crystalline arrays. The self-assembly process can occur (B) in suspension, (C) at the air-liquid interface, (D) on solid supports, and (E) on Langmuir lipid films. (Reprinted from ref. 5 with permission from the publisher; c 1999, Wiley-VCH.)

REFERENCE: 1. Oded Shoseyov, Ilan Levy, Nanobiotechnology BioInspired Devices and Materials of the Future, 2008 Humana Press Inc. 2. Donald K. Martin, Nanobiotechnology of Biomimetic Membranes, 2007 Springer Science + Business Media, LLC. , Protein Nanotechnology - The New Frontier in Biosciences, 2005 Humana Press Inc.

ACKNOWLEDGEMENT Respectable Professor U. B. Sleytr, Professor Paul Messner, Prof. Margit Saara and Prof. Pum are greatly acknowledged. They have been working on bacterial and archeal surface layer glycoproteins and giving inspiration to young microbiologists since 1964. Author is sincerely abide by Dr. R. Selvakumar (PI) for giving such valuable guidance and chance to work on Uranium mine bacterial surface layer proteins as JRF. Indira Gandhi Centre for Atomic Research for their financial support and chance to carried out research on bacterial surface layer proteins. Manuscripts and books publishers are greatly acknowledged.

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