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The Company of Biologists, Journal of Cell Science, 11(113), p. 1963-1971, 2000

DOI: 10.1242/jcs.113.11.1963

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Fa1p is a 171 kDa protein essential for axonemal microtubule severing in Chlamydomonas

Journal article published in 2000 by R. J. Finst, P. J. Kim, Eric R. Griffis ORCID, L. M. Quarmby
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

A key event in deflagellation or deciliation is the severing of the nine outer-doublet axonemal microtubules at a specific site in the flagellar transition zone. Previous genetic analysis revealed three genes that are essential for deflagellation in Chlamydomonas. We have now identified the first of these products, Fa1p, a protein required for Ca(2+)-dependent, axonemal microtubule severing. Genetic mapping and the availability of a tagged allele allowed us to physically map the gene to the centromere-proximal domain of the mating-type locus. We identified clones of Chlamydomonas genomic DNA that rescued the Ca(2+)-dependent axonemal microtubule severing defect of fa1 mutants. The FA1 cDNA, obtained by RT-PCR, encodes a novel protein of 171 kDa, which is predicted to contain an amino-terminal coiled-coil domain and three Ca(2+)/calmodulin binding domains. By western analysis and subcellular fractionation, the FA1 product is enriched in flagellar-basal body complexes. Based on these observations and previous studies, we hypothesize that a Ca(2+)-activated, Ca(2+)-binding protein binds Fa1p leading ultimately to the activation of axonemal microtubule severing.