Stimulation of in vitro motility ofChlamydomonasaxonemes by inhibition of cAMP‐dependent phosphorylation

摘要

AbstractWhen demembranted axonemes ofChlamydomonaswere reactivated with Mg ATP, the proportion of motile axonemes was significantly increased by the preence of either phosphodiesterase (PDE) or protein inhibitor of cAMP‐dependent kinase (PKI). The effect of PDE was cancelled by the addition of cAMP. These findings strongly suggest that the axoneme samples have endogenous cAMP, which can reduce the proportion of motile axonemes via phosphorylation. This inhibitory effect of cAMP onChlamydomonasaxonemes is opposite to its stimulatory effect on the axonemal motility in other organisms so far reported. PKI or PDE activated the motility motility either in the absence of Ca2+, when the axonemes beat with an asymmetric waveform, or in 10−5M Ca2+, when the axonemes beat with a symmetric waveform. This cAMP‐dependent regulation of motility was observed with the axonemes from which detergent‐soluble material had been removed, indicating that the proteins responsible for the regulation still remained in the axonemes. Preliminary in vitro phosphorylation stdies have implicated two polypetides as candidates for the target protein of cAMP‐dependent protein kinase: one with a molecular weight of 270 kD and the other with a much larger molecul