DnaJ family proteins constitute a group of proteins with chaperone function which contain the evolutionarily conserved J domain motif. In this study, a novel cDNA encoding a J Domain Protein (JDP) was investigated from Drosophila melanogaster. Sequence analysis of Drosophila J Domain Protein (dJDP) cDNA with the full coding region revealed that the predicted protein product contains a conserved J domain, but is devoid of additional characteristic structures of DnaJ family proteins, such as G domain or Central Repeat Region (CRR domain). Genomic DNA sequence analysis showed that the dJDP gene consists of five exons, three of which comprise a conserved J domain.
To examine the possible phylogenetic conservation of JDPs in mammals, amino acid sequence similarity search against Expressed Sequence Tag (EST) databases was carried out. Then, full contigs of mouse and human cDNA sequences were constructed. A multiple sequence alignment of JDP orthologs demonstrated that dJDP, human JDP (hJDP), and mouse JDP (mJDP) share considerable homology over the entire protein regions. Comparison of the exonic organization of dJDP with ESTs of differentially spliced hJDP and mJDP transcripts suggested that positions of at least two introns are conserved between insects and mammals.