Protein phosphatases PP1 and PP2A are located in distinct positions in the Chlamydomonas flagellar axoneme

J Cell Sci. 2000 Jan;113 ( Pt 1):91-102.


We postulated that microcystin-sensitive protein phosphatases are integral components of the Chlamydomonas flagellar axoneme, positioned to regulate inner arm dynein activity. To test this, we took a direct biochemical approach. Microcystin-Sepharose affinity purification revealed a prominent 35-kDa axonemal protein, predicted to be the catalytic subunit of type-1 protein phosphatase (PP1c). We cloned the Chlamydomonas PP1c and produced specific polyclonal peptide antibodies. Based on western blot analysis, the 35-kDa PP1c is anchored in the axoneme. Moreover, analysis of flagella and axonemes from mutant strains revealed that PP1c is primarily, but not exclusively, anchored in the central pair apparatus, associated with the C1 microtubule. Thus, PP1 is part of the central pair mechanism that controls flagellar motility. Two additional axonemal proteins of 62 and 37 kDa were also isolated using microcystin-Sepharose affinity. Based on direct peptide sequence and western blots, these proteins are the A- and C-subunits of type 2A protein phosphatase (PP2A). The axonemal PP2A is not one of the previously identified components of the central pair apparatus, outer arm dynein, inner arm dynein, dynein regulatory complex or the radial spokes. We postulate PP2A is anchored on the doublet microtubules, possibly in position to directly control inner arm dynein activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Catalytic Domain
  • Chlamydomonas reinhardtii / cytology
  • Chlamydomonas reinhardtii / enzymology*
  • Chlamydomonas reinhardtii / genetics
  • Chromatography, Affinity
  • Cloning, Molecular
  • Dyneins / metabolism
  • Exons / genetics
  • Flagella / chemistry
  • Flagella / enzymology*
  • Flagella / metabolism
  • Fluorescent Antibody Technique
  • Immune Sera
  • Microcystins
  • Microtubules / enzymology
  • Microtubules / metabolism
  • Molecular Sequence Data
  • Molecular Weight
  • Mutation / genetics
  • Peptides, Cyclic / metabolism
  • Phosphoprotein Phosphatases / chemistry
  • Phosphoprotein Phosphatases / genetics
  • Phosphoprotein Phosphatases / isolation & purification
  • Phosphoprotein Phosphatases / metabolism*
  • Protein Binding
  • Protein Phosphatase 1


  • Immune Sera
  • Microcystins
  • Peptides, Cyclic
  • microcystin
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 1
  • Dyneins

Associated data

  • GENBANK/AF156101