In my experiments, I've seen over 5 times now mCherry fusion proteins (N- and C-terminal) that work fine at ~23-30 C and show progressively less fluorescence at elevated temperatures during in vivo experiments in E. coli. I've not seen any reports of this in the literature, so I'm curious if (1) others have similar anecdotal evidence, (2) I've overlooked anything or (3) there are any mutations that might enhance folding, maturation, etc at 37 C? One of my examples is mCherry inserted into a standard (pBad-d-Topo) commercial expression vector (N-terminal thioredoxin, C-terminal His tag) and everything else is fusions to small bacterial/phage proteins so this isn't limited to esoteric fusion partners. I've seen this effect in minimal media, rich media and on agar plates (e.g. to screen for mutations conferring elevated mCherry fluorescence I'll sometimes recover at 30C or put a plate grown at 37C in the fridge overnight to get brighter fluorescence).
Got same experience and colleges who worked with this protein got also. It is recommended to express mCherry overnight on 4C, but we found another way. We grow culture to optical density 0,3-0,4 and than induce expression on 25-30C. This greatly enhances its folding.
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