Phylogenetic analysis of J domain protein gene

Abstract

Proteins that possess highly specialized signature called J domain are participated in various physiological functions in prokaryotic and eukaryotic cells. They are involved in protein biosynthesis, translocation across cellular membranes, and folding of proteins. In this study, an evolutionarily conserved subclass of JDP (J domain protein) genes from Drosophila melanogaster, mouse, human, Bombyx mori, and Manduca sexta were characterized. Predicted JDP proteins contained the conserved J domain but lacked other structural motifs found in known J domain-containing proteins. Drosophila jdp gene consists of five exons and four introns and encodes two isoforms of 182 and 195 amino acids produced by alternative usage of splicing donor site of intron 4. Northern blot analysis showed that Drosophila jdp gene is expressed in adult heads but not in bodies. RT-PCR analysis revealed that two isoforms are produced in equal amount in adult heads. Orthologous genes from various organisms were identified by comprehensive expressed sequence tags database (dbEST) search. Representative cDNA clones were obtained and their complete sequences were determined. Murine ortholog Jdp1 gene encodes 198 amino acids and is present as a single copy in mouse genome. It is expressed at the highest levels in kidney and at moderate levels in liver, brain, testis, heart, lung, and muscle. However, the transcript was hardly detected in colon or spleen. Human ortholog JDP1 gene encodes two isoforms of 198 and 107 amino acids produced by differential polyadenylation and is present as a single copy in human genome. It is expressed at moderate levels in brain, heart, and testis and at low levels in kidney and stomach. Only the longer isoform of 198 amino acids could be detected by Northern blot analysis. Orthologous jdp genes of two moth species, Bombyx mori and Manduca sexta, encode 170 amino acids. JDP protein sequences of five organisms are highly conserved. The J domain signatures are found at a...