Zagum Bhatti
University of Wisconsin-Milwaukee
Milwaukee, WI
Faculty Mentor: Dr. Pinfen Yang

RSP2 is a component of the radial spoke, a key axonemal structure involved in regulation of dynein-driven flagellar beating. The protein sequence suggests that RSP2 interacts with an array of regulators, including the Ca2+ sensor calmodulin. Furthermore, recombinant RSP2 binds calmodulin in a Ca2+ dependent manner. Based on these results, we proposed that RSP2 mediates the Ca2+-induced flagellar waveform changes via an RSP2/calmodulin complex. To test this, we characterized an RSP2 mutant, pf24, which has incompletely assembled radial spokes, resulting in paralyzed flagella. Through PCR of genomic pf24 DNA and sequencing, it was revealed that a point mutation in pf24 converts the ATG initiation codon to ATA. Western blot analysis of pf24 showed that trace amounts of wild type RSP2 were expressed, suggesting that ATA permits normal translation, albeit inefficiently. In addition, it was shown that pf24 lacks calmodulin supporting our prediction that RSP2 binds calmodulin. This finding also indicates that pf24, an almost null mutant of RSP2, is suitable for transformation rescue experiments by introducing wild type and mutant RSP2 genes.