Highly divergent actin expressed in a Chlamydomonas mutant lacking the conventional actin gene

Biochem Biophys Res Commun. 1998 Oct 9;251(1):71-6. doi: 10.1006/bbrc.1998.9373.


The Chlamydomonas mutant ida5 is deficient in the conventional actin gene and its axoneme lacks a subset of inner dynein arms that contain actin as a subunit. However, this mutant retains some other inner dynein arms because a novel protein (NAP) is expressed as a substitute for actin. In this study, we show by sequence analysis that NAP is identical to a putative actin-related protein, the cDNA sequence of which has recently been reported and shown to have 64% amino acid identity with conventional actin. A polyclonal antibody raised against a synthetic polypeptide corresponding to the NH2-terminal sequence of this protein specifically reacted with the spot corresponding to NAP in two-dimensional electrophoresis patterns. NAP apparently can substitute for conventional actin in some, but not all, cellular functions, and therefore can be regarded as a highly divergent actin. This unconventional actin appears to be expressed only when conventional actin is absent.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / biosynthesis*
  • Actins / genetics*
  • Amino Acid Sequence
  • Animals
  • Chlamydomonas reinhardtii / genetics*
  • Chlamydomonas reinhardtii / immunology
  • Gene Deletion*
  • Genes, Plant
  • Genes, Protozoan
  • Molecular Sequence Data
  • Mutation / genetics*
  • Protozoan Proteins / biosynthesis
  • Protozoan Proteins / genetics


  • Actins
  • Protozoan Proteins