Highly divergent actin expressed in a Chlamydomonas mutant lacking the conventional actin gene.
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.
Kato-Minoura
T
T
National Institute for Basic Biology, Okazaki, 444-8585, Japan.
Uryu
S
S
Hirono
M
M
Kamiya
R
R
D000199:Actins / Q000096:biosynthesis* / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000276:immunology; D017353:Gene Deletion; D017343:Genes, Plant; D017125:Genes, Protozoan; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000235:genetics
D000199:Actins; D015800:Protozoan Proteins