Characterization of the common bed bug's eggshell and egg glue proteins.

An insect egg is one of the most vulnerable stages of insect life, and the evolutionary success of a species depends on the eggshell protecting the embryo and the egg glue securing the attachment. The common bed bug (Cimex lectularius), notorious for its painful and itchy bites, infests human dwellings to feed on blood. They are easier to find these days as they adapt to develop resistance against commonly used insecticides. In this study, we identify and characterize the eggshell protein and the probable egg glue protein (i.e. keratin associated protein 5-10 like protein) of the bed bug by using mass spectrometry and bioinformatics analysis. Furthermore, by using transcription profiling and in vivo RNA interference, we show evidences that the keratin associated protein 5-10 like protein functions as the glue protein. Finally, structural characterizations on the two proteins are performed using recombinant proteins. Amino acid sequences of various insect eggshell and egg glue proteins support their independent evolution among different insect groups. Hence, inhibiting the function of these proteins related to the earliest stage of life can achieve species-specific population control. In this respect, our results would be a starting point in developing new ways to control bed bug population.

Biophysical properties of human body louse nit related proteins: LNSP1, Agp9 and Agp22.

The human parasitic head and body lice lay their eggs on either hair or clothing. Attachments of the eggs are possible because the female lice secret a glue substance from the accessory gland along with the egg, which hardens into a nit sheath that secures and protects the egg (The "nit" commonly refers to either the louse egg with an embryo or the empty hatched egg). Proteins called the louse nit sheath protein (LNSP) are suggested to be the major proteins of the nit sheath, but transcriptome profiling of the accessory glands indicated other proteins such as Agp9 and Agp22 are also expressed in the glands. In this study, human body louse LNSP1 (partial), Agp9, and Agp22 are recombinantly produced using the E. coli expression system, and the biophysical properties characterized. Circular dichroism analysis indicated that the secondary structure elements of LNSP1 N-terminal and middle-domains, Agp9, and Agp22 are prominently random coiled with up to 10-30% anti-parallel ß-sheet element present. Size-exclusion chromatography profiles of LNSP1 proteins further suggested that the ß-sheets made of the smaller N-terminal domain stacks onto the ß-sheets of the larger middle-domain.

Structures of three ependymin-related proteins suggest their function as a hydrophobic molecule binder.

Ependymin was first discovered as a predominant protein in brain extracellular fluid in fish and was suggested to be involved in functions mostly related to learning and memory. Orthologous proteins to ependymin called ependymin-related proteins (EPDRs) have been found to exist in various tissues from sea urchins to humans, yet their functional role remains to be revealed. In this study, the structures of EPDR1 from frog, mouse and human were determined and analyzed. All of the EPDR1s fold into a dimer using a monomeric subunit that is mostly made up of two stacking antiparallel ß-sheets with a curvature on one side, resulting in the formation of a deep hydrophobic pocket. All six of the cysteine residues in the monomeric subunit participate in the formation of three intramolecular disulfide bonds. Other interesting features of EPDR1 include two asparagine residues with glycosylation and a Ca2+-binding site. The EPDR1 fold is very similar to the folds of bacterial VioE and LolA/LolB, which also use a similar hydrophobic pocket for their respective functions as a hydrophobic substrate-binding enzyme and a lipoprotein carrier, respectively. A further fatty-acid binding assay using EPDR1 suggests that it indeed binds to fatty acids, presumably via this pocket. Additional interactome analysis of EPDR1 showed that EPDR1 interacts with insulin-like growth factor 2 receptor and flotillin proteins, which are known to be involved in protein and vesicle translocation.