Display of organophosphorus hydrolase on the cyanobacterial cell surface using synechococcus outer membrane protein a as an anchoring motif.

The display of proteins to cyanobacterial cell surface is made complex by combination of Gram-positive and Gram-negative features of cyanobacterial cell wall. Here, we showed that Synechococcus outer membrane protein A (SomA) can be used as an anchoring motif for the display of organophosphorus hydrolase (OPH) on cyanobacterial cell surface. The OPH, capable of degrading a wide range of organophosphate pesticides, was fused in frame to the carboxyl-terminus of different cell-surface exposed loops of SomA. Proteinase K accessibility assay and immunostaining visualized under confocal laser scanning microscopy demonstrated that a minor fraction of OPH with 12 histidines fused in frame with the third cell-surface exposed loop of SomA (SomAL3-OPH12H) was displayed onto the outermost cell surface with a substantial fraction buried in the cell wall, whereas OPH fused in frame with the fifth cell-surface exposed loop of SomA (SomAL5-OPH) was successfully translocated across the membrane and completely displayed onto the outermost surface of Synechococcus. The successful display of the functional heterologous protein on cell surface provides a useful model for variety of applications in cyanobacteria including screening of polypeptide libraries and whole-cell biocatalysts by immobilizing enzymes.