Partial characterization of the D group proteins of the tubular accessory glands of Tenebrio molitor

Structure of a D-protein gene and amino-acid sequences of the highly repetitive D-proteins secreted by the accessory glands of the mealworm beetle

The D-group proteins form the major component of the proteinaceous secretion of the tubular accessory glands of the yellow mealworm beetle, Tenebrio molitor. In a previous paper, we reported the sequence of two D-protein cDNAs and their inferred translation products. Both proteins contain three highly repetitive domains (A, A' and B). In this paper, we present the cDNA-inferred sequences of 8 more D-proteins, none of which contains an A' domain. We also present the structure of a D-protein gene. Southern analysis suggests that genes coding for an A' domain are relatively rare. Genes with a total of 7 or 8 (A + B domain) repeats seem most common.

The B proteins secreted by the tubular accessory sex glands of the male mealworm beetle, Tenebrio molitor, have sequence similarity to moth pheromone-binding proteins

B proteins represent one of the four major protein groups secreted by the tubular accessory glands of adult, male mealworm beetles. They are acidic proteins with an apparent molecular mass of 18.8 kDa. In this paper we present the deduced amino-acid sequences of two, almost identical B proteins, termed B1 and B2. The mature proteins are 118 amino acids long. They contain 11 (B2) or 12 (B1) possible phosphorylation sites and are rich in glutamic acid (16%). Lectin binding experiments indicate the presence of asparagine linked carbohydrate. The secondary structure of the B proteins is predicted to be almost completely alpha-helical. The B proteins show significant sequence resemblance to a group of pheromone- and odorant-binding proteins in moths and Drosophila, suggesting a role as carrier proteins for lipids.

cDNA-inferred amino-acid sequence of a C protein, a heparin-binding, basic secretion product of the tubular accessory sex glands of the mealworm beetle, Tenebrio molitor

C proteins represent one of the four major protein groups secreted by the tubular accessory glands of male mealworm beetles (Tenebrio molitor). They are basic proteins with an apparent molecular mass of 21.9 kDa. In this paper we present the deduced amino-acid sequence of two, almost identical C proteins, termed C1 and C2. The C proteins contain a consensus sequence for a heparin-binding site, and they are efficiently purified from accessory gland homogenates by heparin-affinity chromatography. No sequence resemblance was found with other proteins in the databases, but their high avidity for heparin suggests a possible involvement of the C proteins in sperm capacitation.

Ordered flow of secretion from accessory glands to specific layers of the spermatophore of mealworm beetles: demonstration with a monoclonal antibody

Monoclonal antibodies were produced against the secretory product of the bean-shaped accessory gland (BAG) of male mealworm beetles (Tenebrio molitor). Antibodies from one clone (PL 6.3) recognized a 9,600 dalton protein with a pI of 6.6 which was found in homogenates of the BAG. The PL 6.3 antigen was first detected on Western blots of BAG proteins from 2-day adults, and amounts increased for the next 6 days until reproductive maturation was achieved. The antibody also recognized a polypeptide with a molecular weight (mw) of about 5,000 daltons which we believe to be derived from the larger 9,600 dalton antigen. There are eight types of secretory cells in the BAG. By using light microscopic immunohistochemistry, we localized the antigens recognized by PL 6.3 in cell type 7 (intense staining) and cell type 5 (weak staining). Results from electron microscopic immunocytochemistry showed that antigen PL 6.3 was concentrated in the secretory granules characteristic of each of these two cell types and was absent in all other cell types. PL 6.3 antigens were traced from the BAG into its secretory product and then into the prespermatophoric mass in the ejaculatory duct. The antigen was not randomly mixed with other secretory products of the accessory glands. As it flowed from the BAG and into the ejaculatory duct, it remained in a coherent, precisely localized mass. Within the definitive spermatophore, the PL 6.3 antigen was concentrated in discrete layers of material that line the lumen.