Characterization of the photochromic pigments in red fluorescent proteins purified from the gut juice of the silkworm Bombyx mori L.
Multiple forms of red fluorescent proteins (RFPs) were observed in the gut juice of the silkworm, Bombyx mori L. It is to be noted that only one RFP band is reported in the literature so far.  However, we report here three electrophoretically separated RFPs (A, B and C) found to be heterogeneous with respect to their components, namely the protein part and the fluorescent tetrapyrrole pigment moiety.  Of the three RFPs, band C was found to be a glycoprotein.  The absorption extinction coefficients and fluorescence quantum yields of the three RFPs were estimated.  Further, this is the first communication demonstrating the presence of three different chlorophyll derivatives associated with the three different RFPs.  The pigments were analyzed by thin layer chromatography followed by their elution to characterize the pigments by spectrophotometric and spectrofluorometric methods.  Spectral characteristics have led to the identification of monovinyl chlorophyllide a, divinyl protochlorophyllide a and monovinyl pheophytin a as being associated with RFP bands A, B and C, respectively.  These three purified RFPs can serve as the source of the three pigments as the standards.