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Title: Rational design of analyte channels of the green fluorescent protein for biosensor applications
Authors: Natta Tansila
Tanawut Tantimongcolwat
Chartchalerm Isarankura-Na-Ayudhya
Chanin Nantasenamat
Virapong Prachayasittikul
Mahidol University
Keywords: Agricultural and Biological Sciences;Biochemistry, Genetics and Molecular Biology;Immunology and Microbiology
Issue Date: 21-Nov-2007
Citation: International Journal of Biological Sciences. Vol.3, No.7 (2007), 463-470
Abstract: A novel solvent-exposed analyte channel, generated by F165G substitution, on the surface of green fluorescent protein (designated His6GFPuv/ F165G) was successfully discovered by the aid of molecular modeling software (PyMOL) in conjunction with site-directed mutagenesis. Regarding the high predictive performance of PyMOL, two pore-containing mutants namely His6GFPuv/H148G and His6GFPuv/H148G/F165G were also revealed. The pore sizes of F165G, H148G, and the double mutant H148G/F165G were in the order of 4, 4.5 and 5.5 Å, respectively. These mutants were subjected to further investigation on the effect of small analytes (e.g. metal ions and hydrogen peroxide) as elucidated by fluorescence quenching experiments. Results revealed that the F165G mutant exhibited the highest metal sensitivity at physiological pH. Meanwhile, the other 2 mutants lacking histidine at position 148 had lower sensitivity against Zn2+and Cu2+than those of the template protein (His6GFPuv). Hence, a significant role of this histidine residue in mediating metal transfer toward the GFP chromophore was proposed and evidently demonstrated by testing in acidic condition. Results revealed that at pH 6.5 the order of metal sensitivity was found to be inverted whereby the H148G/F165G became the most sensitive mutant. The dissociation constants (Kd) to metal ions were in the order of 4.88×10-6M, 16.67×10-6M, 25×10-6M, and 33.33×10-6M for His6GFPuv/F165G, His6GFPuv, His6GFPuv/H148G/F165G and His6GFPuv/ H148G, respectively. Sensitivity against hydrogen peroxide was in the order of H148G/F165G > H148G > F165G indicating the crucial role of pore diameters. However, it should be mentioned that H148G substitution caused a markedly decrease in pH- and thermo-stability. Taken together, our findings rendered the novel pore of GFP as formed by F165G substitution to be a high impact channel without adversely affecting the intrinsic fluorescent properties. This opens up a great potential of using F165G mutant in enhancing the sensitivity of GFP in future development of biosensors. ©Ivyspring International Publisher. All rights reserved.
ISSN: 14492288
Appears in Collections:Scopus 2006-2010

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