Effects of recombinant protein expression on green fluorescent protein diffusion in Escherichia coli

Fluorescence recovery after photobleaching was used to measure the diffusion coefficient of green fluorescent protein (GFP, 27 kDa) in Escherichia coli in the presence or absence of four coexpressed proteins: cytoplasmic maltose binding protein (42 kDa), tau-40 (45 kDa), α-synuclein (14 kDa), or calmodulin (17 kDa). The GFP diffusion coefficient remains constant regardless of the type of coexpresseed protein and whether or not the coexpressed protein was induced. We conclude that expression of these soluble proteins has little to no effect on the diffusion of GFP. These results have implications for the utility of in-cell nuclear magnetic resonance spectroscopy.