We have cloned an unusual colourless green fluorescent protein (GFP)-like protein from Aequorea coerulescens (acGFPL). The A. coerulescens specimens displayed blue (not green) luminescence, and no fluorescence was detected in these medusae. Escherichia coli expressing wild-type acGFPL showed neither fluorescence nor visible coloration. Random mutagenesis generated green fluorescent mutants of acGFPL, with the strongest emitters found to contain an Glu222→Gly (E222G) substitution, which removed the evolutionarily invariant Glu222. Re-introduction of Glu222 into the most fluorescent random mutant, named aceGFP, converted it into a colourless protein. This colourless aceGFP-G222E protein demonstrated a novel type of UV-induced photoconversion, from an immature non-fluorescent form into a green fluorescent form. Fluorescent aceGFP may be a useful biological tool, as it was able to be expressed in a number of mammalian cell lines. Furthermore, expression of a fusion protein of ‘humanized’ aceGFP and β-actin produced a fluorescent pattern consistent with actin distribution in mammalian cells.
A colourless green fluorescent protein homologue from the non-fluorescent hydromedusa Aequorea coerulescens and its fluorescent mutants
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Nadya G. GURSKAYA, Arkady F. FRADKOV, Natalia I. POUNKOVA, Dmitry B. STAROVEROV, Maria E. BULINA, Yurii G. YANUSHEVICH, Yulii A. LABAS, Sergey LUKYANOV, Konstantin A. LUKYANOV; A colourless green fluorescent protein homologue from the non-fluorescent hydromedusa Aequorea coerulescens and its fluorescent mutants. Biochem J 15 July 2003; 373 (2): 403–408. doi: https://doi.org/10.1042/bj20021966
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