Temporin-TR3_2 antimicrobial peptide precursor

Hemocyanin (Hc), a copper-containing extracellular multimeric protein, is the major protein component of hemolymph in different arachnid groups. Hc possesses 7 or 8 very well-characterized types of monomers with molecular weights ranging from 70 to 85 kDa, organized in hexamers or multiple of hexamers. The present chapter compiles the existing data with relation to the function of this protein in the arachnids. Hc has as main function the reversible transport of O2, but it shows many secondary though not less important functions. With reference to this, it has been described that Hc can transport hydrophobic molecules (lipid-derived hormones and lipids) to the different organs, having a key role in the lipid transport system. In arachnids, like in other arthropods and invertebrates, Hc has phenoloxidase function which is related to different metabolic processes such as melanin formation and defense against pathogens. In addition, Hc has additional defensive functions since it can serve as precursor for the production of antimicrobial peptides. In short, the evolution of this protein has led to the development of multiple functions essential for organisms possessing this protein.

Liver-expressed antimicrobial peptide 2 (LEAP-2) is a cationic peptide that plays an important role in innate immunity for host defense. The aim of this study was to characterize the LEAP-2 gene in the Japanese quail (Coturnix japonica). Japanese quail LEAP-2 (CjLEAP-2) was identified from the Japanese quail draft genome database by a local BLAST analysis using chicken LEAP-2 (GgLEAP-2). The exon-intron structure of CjLEAP-2, analyzed from three quails, is composed of three exons, as is the chicken LEAP-2 homolog (GgLEAP-2). An analysis of the coding sequence revealed that CjLEAP-2 is 231 bp long, like GgLEAP-2, and 93% identical to GgLEAP-2 at the nucleic acid level. The predicted amino acid sequence of CjLEAP-2 contained the liver-expressed antimicrobial peptide 2-precursor domain and four cysteine residues characteristic of the LEAP-2 protein. The amino acid sequence of the mature peptide of CjLEAP-2 was 100% identical to that of GgLEAP-2. We confirmed that CjLEAP-2 was transcribed in at least seven tissues, including the digestive system. Additionally, the mature peptide region of CjLEAP-2 exhibited no polymorphisms in 99 quails from six strains. Taken together, these findings indicate that CjLEAP-2 is non-polymorphic and therefore, it likely plays an important role in the innate immunity of quail as it does in chicken.

Antimicrobial peptides (AMPs) constitute a diverse group of compounds that serve a common goal that is host organism defense from infection. Due to their antimicrobial properties, these molecules attract practical interest as potential antibiotics for medical and veterinary use as well as enhancers of plant disease resistance for agriculture. Broad AMP utilization is restricted by the expensiveness of their production using conventional chemical synthesis. For this reason, a number of chimeric genes have been developed for recombinant AMP production in prokaryotes. However, recombinant peptide instability and/or high toxicity to host cells dramatically reduce the yields. In this paper, we review patented strategies of fusion protein design for AMP production. In several cases, the proposed strategies clearly mimic the organization of natural AMP precursor proteins. We describe the main principals of natural AMP precursor organization and fusion constructs adopted and/or artificially designed by man.