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.
Keywords: Chromatin, Drosophila, protamines, protamine-like protein, sperm nuclear basic proteins, SNBP, chromatin condensation, DNA- binding box, protein sequences, spermatogenesis
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