Comparative structural modeling and inference of conserved protein classes in Drosophila seminal fluid

Abstract

The constituents of seminal fluid are a complex mixture of proteins and other molecules, most of whose functions have yet to be determined and many of which are rapidly evolving. As a step in elucidating the roles of these proteins and exposing potential functional similarities hidden by their rapid evolution, we performed comparative structural modeling on 28 of 52 predicted seminal proteins produced in the Drosophila melanogaster male accessory gland. Each model was characterized by defining residues likely to be important for structure and function. Comparisons of known protein structures with predicted accessory gland proteins (Acps) revealed similarities undetectable by primary sequence alignments. The structures predict that Acps fall into several categories: regulators of proteolysis, lipid modifiers, immunity͞ protection, sperm-binding proteins, and peptide hormones. The comparative structural modeling approach indicates that major functional classes of mammalian and Drosophila seminal fluid proteins are conserved, despite differences in reproductive strategies. This is particularly striking in the face of the rapid protein sequence evolution that characterizes many reproductive proteins, including Drosophila and mammalian seminal proteins.

Identity and transfer of male reproductive gland proteins of the dengue vector mosquito, Aedes aegypti: Potential tools for control of female feeding and reproduction

“…Other protein classes that we identified in the putative Ae. aegypti mRGPs have previously been found in male mRGPs of other insects including: chaperones, CRISPs (cysteine-rich secreted proteins), defensins, lectins, lipases, oxidoreductases, RNAses (Mueller et al, 2004;Collins et al, 2006;Walker et al, 2006), and small peptides (Table 1).…”

“…aegypti mRGPs 3.5.A Ae. aegypti mRGP protein classes-One striking feature of male mRGPs is the conservation of protein classes across a wide range of organisms (Mueller et al, 2004;Clark and Swanson, 2005;Braswell et al, 2006;Collins et al, 2006;Davies and Chapman, 2006;Poiani, 2006;Dottorini et al, 2007). The 63 putative Ae.…”

“…aegypti have been attributed to the effect of specific mRGPs in another Diptera species, Drosophila melanogaster (reviewed in Wolfner, 2002;Gillott, 2003;Chapman and Davies, 2004;Wolfner et al, 2005;Wong et al, 2006;. These proteins include: (1) simple peptides, including a "sex peptide" (Acp70A) that induces sexual refractoriness, increases the rate of egg production, and changes the feeding behavior and longevity of female Drosophila (Chapman et al, 2003;Liu and Kubli, 2003;Wigby and Chapman, 2005;Carvalho et al, 2006); (2) "prohormone-like" peptides, one of which (ovulin/Acp26Aa) stimulates ovulation (Heifetz et al, 2000); (3) large glycoproteins which are important for sperm storage (Neubaum and Wolfner, 1999) and other sperm-binding proteins; and (4) proteolysis regulators (Mueller et al, 2004;Ravi Ram et al, 2006;Mueller et al, 2007). Proteins synthesized in the male reproductive tract also have been found to play a role in regulating female post-mating physiology in a broad representation of other arthropods, including muscoid flies (Nelson et al, 1969), moths (Park et al, 1998), and ticks (Weiss and Kaufman, 2004).…”

“…Seminal fluid protein classes are generally conserved across a wide taxonomic range (Mueller et al, 2004;Braswell et al, 2006;Collins et al, 2006;Davies and Chapman, 2006) but several of the proteins themselves evolve more rapidly, on average, than other proteins (Clark et al, 1995;Civetta and Singh, 1999;Civetta and Clark, 2000;Swanson et al, 2001;Swanson and Vacquier, 2002;Clark and Swanson, 2005;Wagstaff and Begun, 2005;Clark et al, 2006;Andrés et al, 2006;Panhuis and Swanson, 2006;Haerty et al, In press). Therefore, it is necessary to identify mRGPs for each species individually.…”

Love hangover

“…Obvious homologues of sex peptide and SPR have not been identified in vertebrates, but this is not surprising given that genes involved in reproduction have a very fast rate of evolution -precisely because they are involved in reproductive behaviour -and this variation promotes the differentiation of species 11 . Although sequence mining has not found much homology along the phylogenetic tree, using more subtle algorithms to analyse protein structure and function indicates that there are fairly striking similarities between components of Drosophila and vertebrate seminal fluid 12 . Perhaps there is yet another reason to use a condom, ladies.…”