Protamine-like proteins in 12 sequenced species of Drosophila

The current study was aimed at analyzing putative protein sequences of the protamine-like proteins of 12 Drosophila species based on the reference sequences of two protamine-like proteins (Mst35Ba and Mst35Bb) found in Drosophila melanogaster sperm nuclei. Protamine-like proteins belong to a larger group of proteins that are involved in DNAbinding known as sperm nuclear basic proteins (SNBPs). SNBPs play a role in chromatin condensation during the postmeiotic stage of spermatogenesis, termed spermiogenesis. During spermiogenesis, nuclear transformation occurs where histones are exchanged for SNBPs, the chromatin condenses, and the nucleus transforms into a needle-like shape in Drosophila. Our goal was to search the 12 sequenced Drosophila genomes for protamine-like proteins based on the known sequences for D. melanogaster. Searches were performed on genomic DNA, mRNA transcripts and amino acid sequences using NCBI basic local alignment search tool (BLAST). Sequence alignments and analysis of amino acid content indicate that homologs for Mst35Ba and Mst35Bb are present in all 12 species of flies analyzed in this study. Functional analyses of a conserved region found within the proteins indicate the presence of a DNA-binding domain, possibly a high mobility group DNA- binding box. This study represents the first large-scale, single-genus dataset for protamine-like proteins and provides the basis for a fine-grained analysis of their evolution.