Identification of a divergent actin-related protein in Drosophila.

The actin-related proteins (ARPs) have primary sequence homology to actin, have no homology to other proteins and, unlike the conventional actins, are clearly divergent. We have identified an ARP in Drosophila that has approximately 30% amino acid identity to most actins, making it the most divergent yet reported. It is also quite divergent from all other ARP sequences. When the Drosophila ARP is aligned with actin it contains sequence insertions, as is the case with all other ARPs. The unique location of the insertions, as well as its overall divergence, indicates it may represent a new isotype. Only one gene was detected by hybridization to both genomic DNA and polytene chromosomes; the location of the gene is 13E on the X chromosome. A transcript of 1350 bases was detected at all stages of development. This transcript was relatively abundant during early embryogenesis, decreasing during the later stages of embryogenesis and increasing again in larvae and adults.