Isolation of a 20-kDa cAMP-dependent phosphoprotein and its putative gene pp20 in Drosophila melanogaster

초록

Although the catalytic subunit of protein kinase A (PKA) is preferentially expressed in the male reproductive organs of Drosophila, the targets of PKA in these organs are poorly studied. Previously, we found three putative PKA substrates (pp45, pp20, and pp10) in the male accessory glands of D. melanogaster. Here, we partially purified pp20 and determined the amino acid sequence of a 12-residue region. A GenBank search based on this partial sequence revealed that this is a novel protein that has not been identified or annotated. A tBLASTn search based on the 12 identified residues yielded a genomic region that putatively encoded the pp20 protein, and an expressed sequence tag (EST) search revealed an EST whose sequence corresponded to that around this genomic region. Using RACE-PCR with this EST sequence, we isolated a full-length cDNA and its putative gene, which we called pp20. The product of pp20 contained all 12 residues identified in pp20, which strongly suggests that pp20 encodes pp20. Interestingly, the expression of pp20 was detected not only in adult male accessory glands but also in all developmental stages, implying that it has biological functions during development in addition to male reproduction.

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