Cloning and isolation of a Conus cysteine-rich protein homologous to Tex31 but without proteolytic activity

The functions of CAP superfamily proteins in mammalian fertility and disease

BACKGROUND

Members of the cysteine-rich secretory proteins (CRISPS), antigen 5 (Ag5) and pathogenesis-related 1 (Pr-1) (CAP) superfamily of proteins are found across the bacterial, fungal, plant and animal kingdoms. Although many CAP superfamily proteins remain poorly characterized, over the past decade evidence has accumulated, which provides insights into the functional roles of these proteins in various processes, including fertilization, immune defence and subversion, pathogen virulence, venom toxicology and cancer biology.

OBJECTIVE AND RATIONALE

The aim of this article is to summarize the current state of knowledge on CAP superfamily proteins in mammalian fertility, organismal homeostasis and disease pathogenesis.

SEARCH METHODS

The scientific literature search was undertaken via PubMed database on all articles published prior to November 2019. Search terms were based on following keywords: 'CAP superfamily', 'CRISP', 'Cysteine-rich secretory proteins', 'Antigen 5', 'Pathogenesis-related 1', 'male fertility', 'CAP and CTL domain containing', 'CRISPLD1', 'CRISPLD2', 'bacterial SCP', 'ion channel regulator', 'CatSper', 'PI15', 'PI16', 'CLEC', 'PRY proteins', 'ASP proteins', 'spermatogenesis', 'epididymal maturation', 'capacitation' and 'snake CRISP'. In addition to that, reference lists of primary and review article were reviewed for additional relevant publications.

OUTCOMES

In this review, we discuss the breadth of knowledge on CAP superfamily proteins with regards to their protein structure, biological functions and emerging significance in reproduction, health and disease. We discuss the evolution of CAP superfamily proteins from their otherwise unembellished prokaryotic predecessors into the multi-domain and neofunctionalized members found in eukaryotic organisms today. At least in part because of the rapid evolution of these proteins, many inconsistencies in nomenclature exist within the literature. As such, and in part through the use of a maximum likelihood phylogenetic analysis of the vertebrate CRISP subfamily, we have attempted to clarify this confusion, thus allowing for a comparison of orthologous protein function between species. This framework also allows the prediction of functional relevance between species based on sequence and structural conservation.

WIDER IMPLICATIONS

This review generates a picture of critical roles for CAP proteins in ion channel regulation, sterol and lipid binding and protease inhibition, and as ligands involved in the induction of multiple cellular processes.

The Dual Prey-Inactivation Strategy of Spiders-In-Depth Venomic Analysis of Cupiennius salei

Most knowledge of spider venom concerns neurotoxins acting on ion channels, whereas proteins and their significance for the envenomation process are neglected. The here presented comprehensive analysis of the venom gland transcriptome and proteome of Cupiennius salei focusses on proteins and cysteine-containing peptides and offers new insight into the structure and function of spider venom, here described as the dual prey-inactivation strategy. After venom injection, many enzymes and proteins, dominated by α-amylase, angiotensin-converting enzyme, and cysteine-rich secretory proteins, interact with main metabolic pathways, leading to a major disturbance of the cellular homeostasis. Hyaluronidase and cytolytic peptides destroy tissue and membranes, thus supporting the spread of other venom compounds. We detected 81 transcripts of neurotoxins from 13 peptide families, whereof two families comprise 93.7% of all cysteine-containing peptides. This raises the question of the importance of the other low-expressed peptide families. The identification of a venom gland-specific defensin-like peptide and an aga-toxin-like peptide in the hemocytes offers an important clue on the recruitment and neofunctionalization of body proteins and peptides as the origin of toxins.

A Recurrent Motif: Diversity and Evolution of ShKT Domain Containing Proteins in the Vampire Snail Cumia reticulata

Proteins of the ShK superfamily are characterized by a small conserved domain (ShKT), first discovered in small venom peptides produced by sea anemones, and acting as specific inhibitors of voltage-dependent and calcium-activated K⁺ channels. The ShK superfamily includes both small toxic peptides and larger multifunctional proteins with various functions. ShK toxins are often important components of animal venoms, where they perform different biological functions including neurotoxic and immunosuppressive effects. Given their high specificity and effectiveness, they are currently regarded as promising pharmacological lead compounds for the treatment of autoimmune diseases. Here, we report on the molecular analysis of ShKT domain containing proteins produced by the Mediterranean vampire snail Cumia reticulata, an ectoparasitic gastropod that feeds on benthic fishes. The high specificity of expression of most ShK transcripts in salivary glands identifies them as relevant components of C. reticulata venom. These ShK proteins display various structural architectures, being produced either as single-domain secretory peptides, or as larger proteins combining the ShKT with M12 or CAP domains. Both ShKT-containing genes and their internal ShKT domains undergo frequent duplication events in C. reticulata, ensuring a high level of variability that is likely to play a role in increasing the range of their potential molecular targets.

Shotgun Proteomics Analysis of Saliva and Salivary Gland Tissue from the Common Octopus Octopus vulgaris

The salivary apparatus of the common octopus ( Octopus vulgaris) has been the subject of biochemical study for over a century. A combination of bioassays, behavioral studies and molecular analysis on O. vulgaris and related species suggests that its proteome should contain a mixture of highly potent neurotoxins and degradative proteins. However, a lack of genomic and transcriptomic data has meant that the amino acid sequences of these proteins remain almost entirely unknown. To address this, we assembled the posterior salivary gland transcriptome of O. vulgaris and combined it with high resolution mass spectrometry data from the posterior and anterior salivary glands of two adults, the posterior salivary glands of six paralarvae and the saliva from a single adult. We identified a total of 2810 protein groups from across this range of salivary tissues and age classes, including 84 with homology to known venom protein families. Additionally, we found 21 short secreted cysteine rich protein groups of which 12 were specific to cephalopods. By combining protein expression data with phylogenetic analysis we demonstrate that serine proteases expanded dramatically within the cephalopod lineage and that cephalopod specific proteins are strongly associated with the salivary apparatus.

An overview of Phoneutria nigriventer spider venom using combined transcriptomic and proteomic approaches

Phoneutria nigriventer is one of the largest existing true spiders and one of the few considered medically relevant. Its venom contains several neurotoxic peptides that act on different ion channels and chemical receptors of vertebrates and invertebrates. Some of these venom toxins have been shown as promising models for pharmaceutical or biotechnological use. However, the large diversity and the predominance of low molecular weight toxins in this venom have hampered the identification and deep investigation of the less abundant toxins and the proteins with high molecular weight. Here, we combined conventional and next-generation cDNA sequencing with Multidimensional Protein Identification Technology (MudPIT), to obtain an in-depth panorama of the composition of P. nigriventer spider venom. The results from these three approaches showed that cysteine-rich peptide toxins are the most abundant components in this venom and most of them contain the Inhibitor Cysteine Knot (ICK) structural motif. Ninety-eight sequences corresponding to cysteine-rich peptide toxins were identified by the three methodologies and many of them were considered as putative novel toxins, due to the low similarity to previously described toxins. Furthermore, using next-generation sequencing we identified families of several other classes of toxins, including CAPs (Cysteine Rich Secretory Protein-CRiSP, antigen 5 and Pathogenesis-Related 1-PR-1), serine proteinases, TCTPs (translationally controlled tumor proteins), proteinase inhibitors, metalloproteinases and hyaluronidases, which have been poorly described for this venom. This study provides an overview of the molecular diversity of P. nigriventer venom, revealing several novel components and providing a better basis to understand its toxicity and pharmacological activities.

Identification of a precursor processing protease from the spider Cupiennius salei essential for venom neurotoxin maturation

Spider venom neurotoxins and cytolytic peptides are expressed as elongated precursor peptides, which are post-translationally processed by proteases to yield the active mature peptides. The recognition motifs for these processing proteases, first published more than 10 years ago, include the processing quadruplet motif (PQM) and the inverted processing quadruplet motif (iPQM). However, the identification of the relevant proteases was still pending. Here we describe the purification of a neurotoxin precursor processing protease from the venom of the spider Cupiennius salei The chymotrypsin-like serine protease is a 28-kDa heterodimer with optimum activity at venom's pH of 6.0. We designed multiple synthetic peptides mimicking the predicted cleavage sites of neurotoxin precursors. Using these peptides as substrates, we confirm the biochemical activity of the protease in propeptide removal from neurotoxin precursors by cleavage C-terminal of the PQM. Furthermore, the PQM protease also cleaves the iPQM relevant for heterodimerization of a subgroup of neurotoxins. An involvement in the maturing of cytolytic peptides is very likely, due to high similarity of present protease recognition motifs. Finally, bioinformatics analysis, identifying sequences of homolog proteins from 18 spiders of 9 families, demonstrate the wide distribution and importance of the isolated enzyme for spiders. In summary, we establish the first example of a PQM protease, essential for maturing of spider venom neurotoxins. In the future, the here described protease may be established as a powerful tool for production strategies of recombinant toxic peptides, adapted to the maturing of spider venom toxins.

Multiomics analysis of the giant triton snail salivary gland, a crown-of-thorns starfish predator

The giant triton snail (Charonia tritonis) is one of the few natural predators of the adult Crown-of-Thorns starfish (COTS), a corallivore that has been damaging to many reefs in the Indo-Pacific. Charonia species have large salivary glands (SGs) that are suspected to produce either a venom and/or sulphuric acid which can immobilize their prey and neutralize the intrinsic toxic properties of COTS. To date, there is little information on the types of toxins produced by tritons. In this paper, the predatory behaviour of the C. tritonis is described. Then, the C. tritonis SG, which itself is made up of an anterior lobe (AL) and posterior lobe (PL), was analyzed using an integrated transcriptomics and proteomics approach, to identify putative toxin- and feeding-related proteins. A de novo transcriptome database and in silico protein analysis predicts that ~3800 proteins have features consistent with being secreted. A gland-specific proteomics analysis confirmed the presence of numerous SG-AL and SG-PL proteins, including those with similarity to cysteine-rich venom proteins. Sulfuric acid biosynthesis enzymes were identified, specific to the SG-PL. Our analysis of the C. tritonis SG (AL and PL) has provided a deeper insight into the biomolecular toolkit used for predation and feeding by C. tritonis.

A combined proteomic and transcriptomic analysis of slime secreted by the southern bottletail squid, Sepiadarium austrinum (Cephalopoda)

Sepiadarium austrinum, the southern bottletail squid, is a small squid that inhabits soft sediments along Australia's south-east coast. When provoked, it rapidly secretes large volumes of slime, presumably as a form of chemical defense. We analyzed the proteomic composition of this slime using tandem mass spectrometry and transcriptomics and found that it was remarkably complex with 1735 identified protein groups (FDR:0.01). To investigate the chemical defense hypothesis we performed an Artemia toxicity assay and used sequence analysis to search for toxin-like molecules. Although the slime did not appear to be toxic to Artemia we found 13 proteins in slime with the hallmarks of toxins, namely cysteine richness, short length, a signal peptide and/or homology to known toxins. These included three short (80-130AA) cysteine rich secreted proteins with no homology to proteins on the NCBI or UniProt databases. Other protein families found included, CAP, phospholipase-B, ShKT-like peptides, peptidase S10, Kunitz BPTI and DNase II. Quantitative analysis using intensity based absolute quantification (iBAQ via MaxQuant) revealed 20 highly abundant proteins, accounting for 67% of iBAQ signal, and three of these were toxin-like. No mucin homologues were found suggesting that the structure of the slime gel may be formed by an unknown mechanism.

BIOLOGICAL SIGNIFICANCE

This study is the first known instance of a slime secretion from a cephalopod to be analyzed by proteomics methods and is the first investigation of a member of the family Sepiadariidae using proteomic methods. 1735 proteins were identified with 13 of these fitting criteria established for the identification of putative toxins. The slime is dominated by 20 highly abundant proteins with secreted, cysteine rich proteins. The study highlights the importance of 'omics approaches in understanding novel organisms.

Salinity influences the biochemical response of Crassostrea angulata to Arsenic

The increasing rate of occurrence and persistence of climatic events causing salinity shifts, in combination with contamination, may further challenge organisms response to environmental stress. Hence, we studied the effects of different salinity levels (10, 20, 30 and 40) on the response of the oyster Crassostrea angulata to Arsenic (As) exposure (4 mg L(-1)). Total As, Na(+) and K(+) concentrations in oyster tissues were determined. Biochemical analysis were performed to assess osmotic regulation (CA), metabolism (ETS), enzymatic (SOD, CAT and GSTs) and non-enzymatic (GSH/GSSG and LPO) markers of oxidative stress. Results obtained showed significantly higher metabolic activities in oysters maintained in low salinity (10) exposure, coupled with higher As accumulation, as well as higher SOD and CAT activities, compared to higher salinities (30 and 40). GSTs activity and LPO levels were higher in oysters exposed to As at salinities 20, 30 and 40, compared to the same conditions without As. From our findings we concluded that the response of C. angulata to As is influenced by salinity. At the lowest salinity (10) oysters accumulated higher As concentrations, here attributed to higher metabolic rate involved in physiological osmoregulation, also stimulating antioxidant related enzymes activity (SOD and CAT) and thus preventing increased LPO (higher ETS activity also observed without As). On the contrary, at salinities 30 and 40 with As, antioxidant SOD and CAT were inhibited, enabling for LPO generation. Given our results, the effects of As on the oysters antioxidant capacity appears to be more deleterious under higher salinities (20, 30 and 40), comparing to salinity 10. The differentiated responses demonstrated in the present study in C. angulata oysters exposed to As under different salinities, bring new insights on the mechanisms of environmental adaptability of this species, namely to salinity shifts, and the interactions between such alterations and As exposure.

The venomous cocktail of the vampire snail Colubraria reticulata (Mollusca, Gastropoda)

Background

Hematophagy arose independently multiple times during metazoan evolution, with several lineages of vampire animals particularly diversified in invertebrates. However, the biochemistry of hematophagy has been studied in a few species of direct medical interest and is still underdeveloped in most invertebrates, as in general is the study of venom toxins. In cone snails, leeches, arthropods and snakes, the strong target specificity of venom toxins uniquely aligns them to industrial and academic pursuits (pharmacological applications, pest control etc.) and provides a biochemical tool for studying biological activities including cell signalling and immunological response. Neogastropod snails (cones, oyster drills etc.) are carnivorous and include active predators, scavengers, grazers on sessile invertebrates and hematophagous parasites; most of them use venoms to efficiently feed. It has been hypothesized that trophic innovations were the main drivers of rapid radiation of Neogastropoda in the late Cretaceous.

We present here the first molecular characterization of the alimentary secretion of a non-conoidean neogastropod, Colubraria reticulata. Colubrariids successfully feed on the blood of fishes, throughout the secretion into the host of a complex mixture of anaesthetics and anticoagulants. We used a NGS RNA-Seq approach, integrated with differential expression analyses and custom searches for putative secreted feeding-related proteins, to describe in detail the salivary and mid-oesophageal transcriptomes of this Mediterranean vampire snail, with functional and evolutionary insights on major families of bioactive molecules.

Results

A remarkably low level of overlap was observed between the gene expression in the two target tissues, which also contained a high percentage of putatively secreted proteins when compared to the whole body. At least 12 families of feeding-related proteins were identified, including: 1) anaesthetics, such as ShK Toxin-containing proteins and turripeptides (ion-channel blockers), Cysteine-rich secretory proteins (CRISPs), Adenosine Deaminase (ADA); 2) inhibitors of primary haemostasis, such as novel vWFA domain-containing proteins, the Ectonucleotide pyrophosphatase/phosphodiesterase family member 5 (ENPP5) and the wasp Antigen-5; 3) anticoagulants, such as TFPI-like multiple Kunitz-type protease inhibitors, Peptidases S1 (PS1), CAP/ShKT domain-containing proteins, Astacin metalloproteases and Astacin/ShKT domain-containing proteins; 4) additional proteins, such the Angiotensin-Converting Enzyme (ACE: vasopressive) and the cytolytic Porins.

Conclusions

Colubraria feeding physiology seems to involve inhibitors of both primary and secondary haemostasis, anaesthetics, a vasoconstrictive enzyme to reduce feeding time and tissue-degrading proteins such as Porins and Astacins. The complexity of Colubraria venomous cocktail and the divergence from the arsenal of the few neogastropods studied to date (mostly conoideans) suggest that biochemical diversification of neogastropods might be largely underestimated and worth of extensive investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1648-4) contains supplementary material, which is available to authorized users.

Conotoxin gene superfamilies

Conotoxins are the peptidic components of the venoms of marine cone snails (genus Conus). They are remarkably diverse in terms of structure and function. Unique potency and selectivity profiles for a range of neuronal targets have made several conotoxins valuable as research tools, drug leads and even therapeutics, and has resulted in a concerted and increasing drive to identify and characterise new conotoxins. Conotoxins are translated from mRNA as peptide precursors, and cDNA sequencing is now the primary method for identification of new conotoxin sequences. As a result, gene superfamily, a classification based on precursor signal peptide identity, has become the most convenient method of conotoxin classification. Here we review each of the described conotoxin gene superfamilies, with a focus on the structural and functional diversity present in each. This review is intended to serve as a practical guide to conotoxin superfamilies and to facilitate interpretation of the increasing number of conotoxin precursor sequences being identified by targeted-cDNA sequencing and more recently high-throughput transcriptome sequencing.

Combined proteomic and transcriptomic interrogation of the venom gland of Conus geographus uncovers novel components and functional compartmentalization

Cone snails are highly successful marine predators that use complex venoms to capture prey. At any given time, hundreds of toxins (conotoxins) are synthesized in the secretory epithelial cells of the venom gland, a long and convoluted organ that can measure 4 times the length of the snail's body. In recent years a number of studies have begun to unveil the transcriptomic, proteomic and peptidomic complexity of the venom and venom glands of a number of cone snail species. By using a combination of DIGE, bottom-up proteomics and next-generation transcriptome sequencing the present study identifies proteins involved in envenomation and conotoxin maturation, significantly extending the repertoire of known (poly)peptides expressed in the venom gland of these remarkable animals. We interrogate the molecular and proteomic composition of different sections of the venom glands of 3 specimens of the fish hunter Conus geographus and demonstrate regional variations in gene expression and protein abundance. DIGE analysis identified 1204 gel spots of which 157 showed significant regional differences in abundance as determined by biological variation analysis. Proteomic interrogation identified 342 unique proteins including those that exhibited greatest fold change. The majority of these proteins also exhibited significant changes in their mRNA expression levels validating the reliability of the experimental approach. Transcriptome sequencing further revealed a yet unknown genetic diversity of several venom gland components. Interestingly, abundant proteins that potentially form part of the injected venom mixture, such as echotoxins, phospholipase A2 and con-ikots-ikots, classified into distinct expression clusters with expression peaking in different parts of the gland. Our findings significantly enhance the known repertoire of venom gland polypeptides and provide molecular and biochemical evidence for the compartmentalization of this organ into distinct functional entities.

A family of secreted pathogenesis-related proteins in Candida albicans

Analysing culture supernatants of yeast and hyphal cells of Candida albicans, we found two close homologues of pathogenesis-related (PR-) 1 proteins, Rbe1p and Rbt4p, in the secretome. Due to sequence homology, three additional, yet not characterized open reading frames, ORF19.6200, ORF19.2787 and ORF19.2336, together with RBE1 and RBT4 were assigned to a novel family of CaPRY proteins. In a Δrbe1/Δrbt4 deletion strain, genome-wide transcriptional analysis revealed differential transcription of only a limited set of genes implicated in virulence and oxidative stress response. Single deletion of RBE1 or RBT4 in a clinical C. albicans isolate resulted in a moderate but significant attenuation in virulence in a mouse model for disseminated candidiasis. However, a synergistic effect was observed in a Δrbe1/Δrbt4 double deletion strain, where virulence was strongly affected. Remarkably, transcription of RBT4 and RBE1 was each upregulated in blastospores of Δrbe1 or hyphae of Δrbt4 deletion strains respectively, indicating functional complementation thereby compensating a potential virulence defect in the single deletion strains. Furthermore, the double deletion strain showed increased sensitivity to attack by polymorphonuclear leucocytes. Therefore, the crucial contribution of both C. albicans pathogenesis-related proteins to virulence might be vested in protection against phagocyte attack.

Transcriptomic responses to salinity stress in the Pacific oyster Crassostrea gigas

BACKGROUND

Low salinity is one of the main factors limiting the distribution and survival of marine species. As a euryhaline species, the Pacific oyster Crassostrea gigas is considered to be tolerant to relative low salinity. The genes that regulate C. gigas responses to osmotic stress were monitored using the next-generation sequencing of whole transcriptome with samples taken from gills. By RNAseq technology, transcript catalogs of up- and down-regulated genes were generated from the oysters exposed to low and optimal salinity seawater.

METHODOLOGY/PRINCIPAL FINDINGS

Through Illumina sequencing, we reported 1665 up-regulated transcripts and 1815 down-regulated transcripts. A total of 45771 protein-coding contigs were identified from two groups based on sequence similarities with known proteins. As determined by GO annotation and KEGG pathway mapping, functional annotation of the genes recovered diverse biological functions and processes. The genes that changed expression significantly were highly represented in cellular process and regulation of biological process, intracellular and cell, binding and protein binding according to GO annotation. The results highlighted genes related to osmoregulation, signaling and interactions of osmotic stress response, anti-apoptotic reactions as well as immune response, cell adhesion and communication, cytoskeleton and cell cycle.

CONCLUSIONS/SIGNIFICANCE

Through more than 1.5 million sequence reads and the expression data of the two libraries, the study provided some useful insights into signal transduction pathways in oysters and offered a number of candidate genes as potential markers of tolerance to hypoosmotic stress for oysters. In addition, the characterization of C. gigas transcriptome will not only provide a better understanding of the molecular mechanisms about the response to osmotic stress of the oysters, but also facilitate research into biological processes to find underlying physiological adaptations to hypoosmotic shock for marine invertebrates.

Recruitment of glycosyl hydrolase proteins in a cone snail venomous arsenal: further insights into biomolecular features of Conus venoms

Cone snail venoms are considered an untapped reservoir of extremely diverse peptides, named conopeptides, displaying a wide array of pharmacological activities. We report here for the first time, the presence of high molecular weight compounds that participate in the envenomation cocktail used by these marine snails. Using a combination of proteomic and transcriptomic approaches, we identified glycosyl hydrolase proteins, of the hyaluronidase type (Hyal), from the dissected and injectable venoms (“injectable venom” stands for the venom variety obtained by milking of the snails. This is in contrast to the “dissected venom”, which was obtained from dissected snails by extraction of the venom glands) of a fish-hunting cone snail, Conus consors (Pionoconus clade). The major Hyal isoform, Conohyal-Cn1, is expressed as a mixture of numerous glycosylated proteins in the 50 kDa molecular mass range, as observed in 2D gel and mass spectrometry analyses. Further proteomic analysis and venom duct mRNA sequencing allowed full sequence determination. Additionally, unambiguous segment location of at least three glycosylation sites could be determined, with glycans corresponding to multiple hexose (Hex) and N-acetylhexosamine (HexNAc) moieties. With respect to other known Hyals, Conohyal-Cn1 clearly belongs to the hydrolase-type of Hyals, with strictly conserved consensus catalytic donor and positioning residues. Potent biological activity of the native Conohyals could be confirmed in degrading hyaluronic acid. A similar Hyal sequence was also found in the venom duct transcriptome of C. adamsonii (Textilia clade), implying a possible widespread recruitment of this enzyme family in fish-hunting cone snail venoms. These results provide the first detailed Hyal sequence characterized from a cone snail venom, and to a larger extent in the Mollusca phylum, thus extending our knowledge on this protein family and its evolutionary selection in marine snail venoms.

Specialisation of the venom gland proteome in predatory cone snails reveals functional diversification of the conotoxin biosynthetic pathway

Conotoxins, venom peptides from marine cone snails, diversify rapidly as speciation occurs. It has been suggested that each species can synthesize between 1000 and 1900 different toxins with little to no interspecies overlap. Conotoxins exhibit an unprecedented degree of post-translational modifications, the most common one being the formation of disulfide bonds. Despite the great diversity of structurally complex peptides, little is known about the glandular proteins responsible for their biosynthesis and maturation. Here, proteomic interrogations on the Conus venom gland led to the identification of novel glandular proteins of potential importance for toxin synthesis and secretion. A total of 161 and 157 proteins and protein isoforms were identified in the venom glands of Conus novaehollandiae and Conus victoriae, respectively. Interspecies differences in the venom gland proteomes were apparent. A large proportion of the proteins identified function in protein/peptide translation, folding, and protection events. Most intriguingly, however, we demonstrate the presence of a multitude of isoforms of protein disulfide isomerase (PDI), the enzyme catalyzing the formation and isomerization of the native disulfide bond. Investigating whether different PDI isoforms interact with distinct toxin families will greatly advance our knowledge on the generation of cone snail toxins and disulfide-rich peptides in general.

Epitope mapping and identification on a 3D model built for the tartary buckwheat allergic protein TBb

Allergic protein TBb, a major allergen in tartary buckwheat, was divided into four epitope-containing fragments and was named F1, F2, F3, and F4, respectively. Results of immunological assays revealed that F2 had the strongest IgE-binding activity to patient's sera, which indicated that it might contain the linear IgE-binding epitope of TBb. According to the results of sequence analysis and molecular modeling of tartary buckwheat allergen, three mutants of F2 gene (R139A, R141A, and D144A) were reconstructed using site-directed mutagenesis, and each mutant was expressed in Escherichia coli BL21 (DE3). Following purification by Ni(2+) affinity chromatography, enzyme-linked immunosorbent assay and dot blot were performed for wild-type F2 and its mutants using sera from buckwheat-allergic patients and a negative control (non-allergic patient). Results showed that mutants R139A and D144A had weaker IgE-binding activity to patient's sera than wild-type F2, implying that Arg(139) and Asp(144) might be involved in the allergic activity of TBb. However, R141A had the weakest IgE-binding activity, suggesting that Arg(141) may be the critical amino acid of TBb. This is the first report on the epitope mapping and identification of TBb. Our findings will contribute to the production of TBb hypoallergens and to allergen-specific immunotherapy for tartary buckwheat allergy.

The CAP superfamily: cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins--roles in reproduction, cancer, and immune defense

The cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins (CAP) superfamily members are found in a remarkable range of organisms spanning each of the animal kingdoms. Within humans and mice, there are 31 and 33 individual family members, respectively, and although many are poorly characterized, the majority show a notable expression bias to the reproductive tract and immune tissues or are deregulated in cancers. CAP superfamily proteins are most often secreted and have an extracellular endocrine or paracrine function and are involved in processes including the regulation of extracellular matrix and branching morphogenesis, potentially as either proteases or protease inhibitors; in ion channel regulation in fertility; as tumor suppressor or prooncogenic genes in tissues including the prostate; and in cell-cell adhesion during fertilization. This review describes mammalian CAP superfamily gene expression profiles, phylogenetic relationships, protein structural properties, and biological functions, and it draws into focus their potential role in health and disease. The nine subfamilies of the mammalian CAP superfamily include: the human glioma pathogenesis-related 1 (GLIPR1), Golgi associated pathogenesis related-1 (GAPR1) proteins, peptidase inhibitor 15 (PI15), peptidase inhibitor 16 (PI16), cysteine-rich secretory proteins (CRISPs), CRISP LCCL domain containing 1 (CRISPLD1), CRISP LCCL domain containing 2 (CRISPLD2), mannose receptor like and the R3H domain containing like proteins. We conclude that overall protein structural conservation within the CAP superfamily results in fundamentally similar functions for the CAP domain in all members, yet the diversity outside of this core region dramatically alters target specificity and, therefore, the biological consequences.