Characterization of flavin binding in flagella of Chlamydomonas

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