THE DROSOPHILA MOLYBDENUM COFACTOR GENE CINNAMON IS HOMOLOGOUS TO 3 ESCHERICHIA-COLI COFACTOR PROTEINS AND TO THE RAT PROTEIN GEPHYRIN

Essentially all organisms depend upon molybdenum oxidoreductases which require a molybdopterin cofactor for catalytic activity. Mutations re sulting in a lack of the cofactor show a pleiotropic loss of molybdoen zyme activities and thereby define genes involved in cofactor biosynth esis or utilization. In prokaryotes, two operons are directly associat ed with biosynthesis of the pterin moiety and its side chain while add itional loci play a role in the acquisition of molybdenum and/or activ ation of the cofactor. Here we report the cloning of cinnamon, a Droso phila molybdenum cofactor gene encoding a protein with sequence simila rity to three of the prokaryotic cofactor proteins, In addition, the D rosophila cinnamon protein is homologous to gephyrin, a protein isolat ed from the rat central nervous system. Our results suggest that some portions of the prokaryotic cofactor biosynthetic pathway composed of monofunctional proteins have evolved into a multifunctional protein in higher eukaryotes.