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A unique antibody-binding protein, (E12B2)n, was genetically synthesized, which was characterized by a hydrophobic peptide, E12, at one terminus and an antibody-binding peptide, B2, at the other. It was clarified by atomic force microscopy (AFM) imaging that this protein was efficiently self-assembled on a hydrophobic solid surface. (E12B2)n self-assembled on a microplate exhibited an excellent performance of antibody-binding affinity. The proposed design of antibody-binding protein seems promising in immobilizing antibody molecules on hydrophobic solid surfaces.

A fusion protein consisting of human calmodulin (CaM) and glutathione S-transferase (GST) was produced by gene fusion. The fusion protein was overexpressed in Escherichia coli as a soluble form and purified with one-step affinity chromatography using glutathione-Sepharose. The protein had the modulating activity of CaM and the binding capability to glutathione of GST. Phosphodiesterase, which is a CaM dependent enzyme, was activated by the fusion protein, with the Ca2+ level equal to the level equivalent to a native CaM. Furthermore, CaM could be immobilized on a solid-phase matrix through the use of GST moiety while its modulating activity was retained. Phosphodiesterase activity was switched on and off by the immobilized CaM with or without Ca2+, and repeated use of CaM was demonstrated.

Calmodulin (CaM), a calcium ion sensitive protein, was conjugated with dioctadecyldimethylammonium bromide and subsequently assembled into a monolayer at the air-water interface using the LB method. The lipid-conjugated calmodulin (LCC) retains its calcium sensitivity, determined from the changes in the area-pressure isotherm of the monolayer obtained at the air-water interface. The functionality of this protein assembly was characterized by the activation of phosphodiesterase (PDE), a CaM responsive enzyme. The enzyme activity of PDE coupled with LCC at the air-water interface was measured by using the enzymatic method. It was found that LCC retained its enzyme activity modulating function of calmodulin, which is triggered by calcium ions. This characteristic plays an important role in fabricating molecular assembly of proteins which have a cooperative interaction at the molecular level.