alpha-Amidated peptides: approaches for analysis

A reexamination of poneratoxin from the venom of the bullet ant Paraponera clavata

In 1991, Piek et al. [45] described a voltage-gated sodium channel (VGSC) modifier from "bullet ant" (Paraponera clavata) venom they called poneratoxin (PoTx). Using UV chromatography and Edman degradation they showed two "identical peptides" of 25 residues. We reinvestigated PoTx using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-TMS). De novo sequencing showed the two peptides were actually structurally different peptides: the originally described PoTx and a glycyl pro-peptide (glycyl-PoTx) that lacks C-terminus amidation. We examined P. clavata venom from different geographical locations and discovered two additional PoTx analogs: an A23E substitution analog and a D22N; A23V substitutions analog. We tested PoTx and these three natural analogs on the mammalian sensory voltage-gated sodium channel, Na_v1.7, using whole cell voltage-clamp. PoTx and each analog induced slowly activating currents in response to small depolarizing steps and sustained currents due to blockade of channel inactivation, similar to that described previously in skeletal muscle [19]. Glycyl-PoTx had the same potency and efficacy as PoTx. A23E PoTx, with a decrease in both C-terminal net positive charge and hydrophobicity, had an eight-fold reduction in potency compared to PoTx. In contrast, the D22N; A23V PoTx, with an increase in both C-terminal net positive charge and hydrophobicity, had a nearly five-fold increase in potency compared to PoTx. We found that changes in PoTx C-terminus caused a significant change in PoTx potency.

cDNA CLONING AND TRANSCRIPTIONAL REGULATION OF THE CECROPIN AND ATTACIN FROM THE ORIENTAL FRUIT FLY, Bactrocera dorsalis (DIPTERA: TEPHRITIDAE)

We described the cDNA cloning of two antimicrobial peptides (AMPs), cecropin (BdCec), and attacin C (BdAttC), from the oriental fruit fly, Bactrocera dorsalis (Hendel), a serious insect pest of fruit trees. Using rapid amplification of cDNA ends, fragments encompassing the entire open reading frames of BdCec and BdAttC were cloned and sequenced. The complete 425 bp cDNA of BdCec encodes a protein of 64 amino acids with a predicted molecular weight of 6.84 kDa. The 931 bp cDNA of BdAttC encodes a protein of 239 residues with a predicted molecular weight of 24.97 kDa. Real-time quantitative RT-PCR demonstrated that the developmental transcription profiles of BdCec and BdAttC were similar in each larvae, pupae, and adults. The constitutive expression levels of both AMPs were high in the first-instar and late third-instar larvae, suggesting that their antimicrobial activity is active in the newly hatched larvae and just before pupation. The basal expression levels were not significant different in adult fat bodies. The expression of BdCec and BdAttC was upregulated after bacterial challenge in adult fat bodies. The ratio of inducible expression to constitutive expression was lower in males compared to females.

Antimicrobial peptides: key components of the innate immune system

Life-threatening infectious diseases are on their way to cause a worldwide crisis, as treating them effectively is becoming increasingly difficult due to the emergence of antibiotic resistant strains. Antimicrobial peptides (AMPs) form an ancient type of innate immunity found universally in all living organisms, providing a principal first-line of defense against the invading pathogens. The unique diverse function and architecture of AMPs has attracted considerable attention by scientists, both in terms of understanding the basic biology of the innate immune system, and as a tool in the design of molecular templates for new anti-infective drugs. AMPs are gene-encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially, which exhibit broad spectrum antimicrobial activity. AMPs have been the subject of natural evolution, as have the microbes, for hundreds of millions of years. Despite this long history of co-evolution, AMPs have not lost their ability to kill or inhibit the microbes totally, nor have the microbes learnt to avoid the lethal punch of AMPs. AMPs therefore have potential to provide an important breakthrough and form the basis for a new class of antibiotics. In this review, we would like to give an overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals, in addition to pharmaceutical aspects and the additional functions of AMPs.

C12ORF39, a novel secreted protein with a typical amidation processing signal

In the present study we describe a novel secreted protein, named C12ORF39 (chromosome 12 open-reading framework 39), which contains a typical amidation/proteolytic processing signal (Gly–Arg–Arg motif). Interestingly, C12ORF39 protein is not hydrolysed, but is a full-length protein without signal peptides. Western blotting indicated that c-Myc-tagged C12ORF39 is secreted into culture medium in transfected HeLa cells. Quantitative RT-PCR (reverse transcription-PCR) analysis revealed that c12orf39 is mainly expressed in placenta and brain. Immunohistochemistry on formalin-fixed paraffin-embedded human term placenta using a rabbit antibody against human C12ORF39 demonstrated that the protein was localized extracellularly, surrounding the trophoblastic cells. In addition, C12ORF39 secretion could be blocked by brefeldin A, suggesting that the secretion of C12ORF39 is dependent on the Golgi apparatus. Furthermore, laser-scanning confocal microscopy also confirmed that the C12ORF39 protein co-localized with the Golgi apparatus. Taken together, although C12ORF39 is not a secreted small peptide, it can also be secreted to play a role in the biological functions of the placenta.