Ef. Smith et Pa. Lefebvre, PF16 ENCODES A PROTEIN WITH ARMADILLO REPEATS AND LOCALIZES TO A SINGLE MICROTUBULE OF THE CENTRAL APPARATUS IN CHLAMYDOMONAS FLAGELLA, The Journal of cell biology, 132(3), 1996, pp. 359-370
Several studies have indicated that the central pair of microtubules a
nd their associated structures play a significant role in regulating f
lagellar motility. To begin a molecular analysis of these components w
e have generated central apparatus-defective mutants in Chlamydomonas
reinhardtii using insertional mutagenesis. One paralyzed mutant recove
red in our screen, D2, is an allele of a previously identified mutant,
pf16. Mutant cells have paralyzed flagella, and the C1 microtubule of
the central apparatus is missing in isolated axonemes. We have cloned
the wild-type PF16 gene and confirmed its identity by rescuing pf16 m
utants upon transformation. The rescued pf16 cells were wild-type in m
otility and in axonemal ultrastructure. A full-length cDNA clone for P
F16 was obtained and sequenced. Database searches using the predicted
566 amino acid sequence of PF16 indicate that the protein contains eig
ht contiguous armadillo repeats. A number of proteins with diverse cel
lular functions also contain armadillo repeats including pendulin, Rch
1, importin, SRP-1, and armadillo. An antibody was raised against a fu
sion protein expressed from the cloned cDNA. Immunofluorescence labeli
ng of wild-type flagella indicates that the PF16 protein is localized
along the length of the flagella while immunogold labeling further loc
alizes the PF16 protein to a single microtubule of the central pair. B
ased on the localization results and the presence of the armadillo rep
eats in this protein, we suggest that the PF16 gene product is involve
d in protein-protein interactions important for C1 central microtubule
stability and flagellar motility.