Each monomer of the trimeric outer membrane porin OmpF of Salmonella typhi folds as a 16-stranded β-barrel with eight short turns at the periplasmic side and eight loops on the cell surface side. Yellow fluorescent protein (YFP) has been engineered into Loop 7 of OmpF. HindIII and EcoRV restriction sites were introduced in the region corresponding to Loop 7 of ompF gene. Flanking the sites yfp gene amplified from pEYFP, was inserted with 15 bases as linker on either side of the insert. The chimeric protein product was successfully expressed in E. coli BL21 (DE3). The strategy has provided a hybrid protein in which an outer membrane protein presents a yellow fluorescent protein. This fluorescent chimera can be used as a marker for biological analysis. Moreover, the hydrophilic component makes the engineered membrane protein more amenable for crystallographic analysis, as it improves the crystallisation potential due to the globular component.
Key words: Membrane protein, OmpF, Salmonella typhi, yellow fluorescent protein (YFP).
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