Characterization of flavin binding in flagella of Chlamydomonas

Using an experimental approach similar to that used for Euglena flagella, we found that flagella and flagellar membrane preparations (isoagglutinins) of the unicellular green algae Chlamydomonas moewusii and C. reinhardtii, but not cells without flagella, bind radiolabelled riboflavin with high affinity and specificity. In addition, flagella and isoagglutinins contain high amounts of methanol-extractable flavins. These results indicate an abundance of proteins with high affinity for riboflavin in the flagella. Since sexual adhesiveness of gametic flagella in C. moewusii is controlled by light, the possibility is discussed that flavoproteins in the flagella are involved in this reaction. Action spectra exhibit maxima at 450 and 600 nm, suggesting - at least for the 450 nm band - a typical blue-light receptor.