Model protein-cell system

Whilst numerous real fermentation broths have been studied [18-20], a popular model protein-cell system is the mixture of washed yeast cells and bovine serum... 

Ling, G. N. All-or-none adsorption by living cells and model protein-water systems discussion of the problem of "permease-induction" and determination of secondary and tertiary structure of proteins. Fed. Proc. 1966, 25, 958-978. 

Dunlop [18] proposed a model for sub-lytic effects in plant cells, based on the same principles, but including four properties postulated to be of particular importance in these systems, namely calcium ion flux, osmo-regulation, cell-cell contact/aggregation and stress protein expression. Of these factors, osmo-regulation (and its inter-relationship with the cell wall) and aggregation patterns, in particular, distinguish plant cells from mammalian cell systems. 

Today, there are a wide variety of laboratory protein expression systems available, ranging from cell-free systems over bacterial and yeast cultures to eukaryotic models including the Xenopus oocytes or insect and mammalian cell cultures, some of which even form polarised epithelial-like cells layers. In Table 24.1, an overview of the most important systems, as well as their particular strength and weaknesses in the expression of transmembrane transport proteins is provided. 

There are no inherent limitations to the nature of the interaction that can be probed with the FAC method. This too stems from an uncoupling of the binding event and the detector. The method can be applied to simple binary interactions between protein and small molecule, but also to protein-protein interactions, protein-cell interactions and virtually any interaction that can be modeled in a flow system. Some of the more elegant examples include drug interaction with whole cells [12] and membrane-bound receptors from brain homogenates [13]. Ultimately, the limitations are dictated by what can be detected from a stream of column effluent. 

Recently, a putative olfactory receptor from Drosophila, Or43a (Clyne et al., 1999 Vosshall et al., 1999), has been expressed in Xenopus laevis oocytes (Wetzel et al., 2001). The receptor expressed in a heterologous cell system was activated by four odorants, i.e. cyclohexanone, cyclohexanol, benzaldehyde, and benzyl alcohol (Wetzel et al., 2001). These experiments not only provided direct evidence for the function of the Or gene, but also demonstrated that the olfactory receptor can be stimulated without an odorant-binding protein. It was demonstrated earlier that PBP was not necessary to obtain pheromone-dependent responses in cultured olfactory receptor neurons of Manduca sexta (Stengl et al., 1992). The possibility that OBPs have been produced in vitro and were present in cultured ORNs could not be excluded. The same argument can not be raised for the heterologous expression of the Drosophila olfactory receptor. While the evidence that Xenopus oocytes responded to odorants in the absence of OBPs does not support the OBP-odorant complex model, it also demonstrated that OBPs are essential for the kinetics of the olfactory system (see below). 

Aloy, P. and Russell, R.B. (2006) Stmctural systems biology modelling protein interactions. Nat. Rev. Mol. Cell Biol. 7, 188-197. 

Generative models can provide a high-resolution map for protein location. The availability of these maps should aid systems biology modeling of cell behavior. 

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