Cracks in the β-can:: Fluorescent proteins from Anemonia sulcata (Anthozoa, Actinaria)

We characterize two green fluorescent proteins (GFPs), an orange fluorescent protein, and a nonfluorescent red protein isolated from the sea anemone Anemonia sulcata. The orange fluorescent protein and the red protein seem to represent two different states of the same protein. Furthermore. we describe the cloning of a GFP and a nonfluorescent red protein. Both proteins are homologous to the GFP from Aequorea victoria. The red protein is significantly smaller than other GFP homologues, and the formation of a closed GFP-like beta -can is not possible. Nevertheless, the primary structure of the red protein carries all features necessary for orange fluorescence. We discuss a type of beta -can that could be formed in a multimerization process.