Characterizing Dicyanin, a novel Blue Copper Protein

Abstract

Blue Copper Binding (BCB) Proteins are an important family of proteins found in every kingdom of life with a bewildering diversity of functions. Important examples of BCB protein function include pollen tube growth in angiosperm fertilization, signal transduction, and participation in myriad redox reactions throughout the domains of life (especially electron transport chains). Phylogenetic analysis of known BCB proteins in distantly related organisms suggests that this broad family of proteins emerged early in prokaryotic evolution, and has since diverged into many structurally and functionally distinct subfamilies. Much information about the evolution and genesis of existing BCB proteins, as well as identification and preliminary classification of new BCB candidates, can be done using genetic sequence information available in gene databanks in conjunction with specialized software to sort and analyze this data. Using these techniques, a novel BCB candidate was identified in the lycopersicum esculentum displaying some canonical sequence markers in addition to wholly unique regions that suggest previously uncharacterized functionality. Analysis of living tissue mRNAs confirm that this new protein, dubbed dicyanin, is expressed in this organism in all tissues, confirming biological importance. Dicyanin is also interesting because of its genetic structure which features a dual domain motif absent in all known BCBs. This dual domain is theorized to bind two copper ions in a cooperative relationship for unknown reasons, and provides a unique window to trace a branch of BCB evolution with great confidence and precision. For these reasons this project has focused on two goals: 1) to purify and characterize dicyanin to determine its native structure and function and 2) to trace the evolution of dicyanin and homologous proteins through all available gene sequence information.