ARABIDOPSIS NPH1 - A PROTEIN-KINASE WITH A PUTATIVE REDOX-SENSING DOMAIN

The NPH1 (nonphototropic hypocotyl 1) gene encodes an essential compon ent acting very early in the signal-transduction chain for phototropis m. Arabidopsis NPH? contains a serine-threonine kinase domain and LOV1 and LOV2 repeats that share similarity (36 to 56 percent) with Haloba cterium salinarium Bat, Azotobacter vinelandii NIFL, Neurospora crassa White Collar-1, Escherichia call Aer, and the fag family of potassium -channel proteins from Drosophila and mammals. Sequence similarity wit h a known (NIFL) and a suspected (Aer) flavoprotein suggests that NPH1 LOV1 and LOV2 may be flavin-binding domains that regulate kinase acti vity in response to blue light-induced redox changes.