In the native state, four molecules of IrisFP join together to form a tetramer, creating problems for fusion-protein applications. To get round this, the researchers have now modified the protein by introducing four mutations. This makes individual IrisFP molecules (monomers) more stable, reducing their tendency for form tetramers.
"The monomeric variant, mIrisFP, maintains dual photoactivation capacity and has excellent properties as a genetically encoded fluorescent marker protein," explained Wiedenmann.
To test the usefulness of mIrisFP, the researchers genetically fused it with a number of other proteins within cultured cells. These included transcription factors, which regulate the expression of genes within the cell nucleus, and constituent proteins of the cell skeleton ('cytoskeleton'). In all cases, the fusion proteins functioned normally.
Further experiments demonstrated that mIrisFP fusion proteins could, as hoped, be used to study dynamical processes within live cells with a spatial resolution beyond the limits of conventional light microscopy. Specifically, the researchers successfully combined so-called pulse-chase experiments with photoactivation localisation microscopy (PALM) imaging to follow the movement of fluorescently marked fusion proteins over time and at very high spatial resolution.
"The dual photoactivation capability and the monomeric nature of mIrisFP should allow cell biologists to perform a wider range of experiments than possible using only conventional PA-FPs," said Wiedenmann.
"Marine animals such as corals and anemones are not only beautiful and important for ecosystem functioning, but also as source of fluorescent proteins of enormous value to biomedical re
|Contact: Dr. Rory Howlett|
National Oceanography Centre, Southampton (UK)