Figure 5

Properties of GFP with an N-terminal MBP-GS fusion. Lysate supernatants from cultures expressing GFP alone (a) or the MBP-GS-GFP fusion (b) were applied to amylose columns. The green fluorescent product was not retained on the "GFP" column when column buffer was applied, but rather appeared in the first wash eluate (c). In contrast the green fluorescent product was retained on the "MBP-GS-GFP" column when column buffer was applied (c). The protein purification process for MBP-GS-GFP was monitored using SDS-PAGE: Lane 1, cell lysate ("load"); Lane 2, first wash eluate ("wash"); Lane 3, maltose eluate ("elute") (d). Mass spectroscopy confirmed that the band at ~67 kDa was MBP-GS-GFP and identified the minor contaminant at the top of Lane 3 ("elute") as a dimer form. The dimer is known to be a normal occurrence with this construct [69, 70].