Mass spectrometry based approach for identification and characterisation of fluorescent proteins from marine...

We present here a new analytical strategy for identification and characterisation of fluorescent proteins from marine organisms. By applying basic proteomics tools it is possible to screen large sample collections for fluorescent proteins of desired characteristics prior to gene cloning. Our methodology which includes isolation, spectral characterisation, stability testing, gel-based separation and mass spectrometric identification was optimised on samples collected during the Danish Galathea 3 expedition. Four corals of the Fungia, Sarcophyton and Acropora species emitting green fluorescence were tested. Each of the fluorescent extracts behaves differently under denaturing conditions but complete fluorescence loss was not observed. Optimised electrophoretic conditions yielded effective separation of active fluorescent proteins in both 1DE and 2DE. Mass spectrometric analysis of the proteins in the fluorescent spots excised directly from unstained 2DE gels provides sequence information that might be sufficient to design degenerate primers for gene cloning. Identified fluorescent proteins are in agreement with the coral species determined by visual examination of the samples. The presented methodology is a viable alternative to direct gene cloning for the discovery of novel fluorescent proteins and will be further validated on other samples collected during the Galathea 3 expedition.