Toward the mechanism of jarastatin (rJast) inhibition of the integrin αVβ3

Disintegrins are a family of cysteine-rich small proteins that were first identified in snake venom. The high divergence of disintegrins gave rise to a plethora of functions, all related to the interaction with integrins. Disintegrins evolved to interact selectively with different integrins, eliciting many physiological outcomes and being promising candidates for the therapy of many pathologies. We used NMR to determine the structure and dynamics of the recombinant disintegrin jarastatin (rJast) and its interaction with the cancer-related integrin αVβ3. rJast displayed the canonical fold of a medium-sized disintegrin and showed complex dynamic in multiple timescales. We used NMR experiments to map the interaction of rJast with αVβ3, and molecular docking followed by molecular dynamics (MD) simulation to describe the first structural model of a disintegrin/integrin complex. We showed that not only the RGD loop participates in the interaction, but also the N-terminal domain. rJast plasticity was essential for the interaction with αVβ3 and correlated with the main modes of motion depicted in the MD trajectories. In summary, our study provides novel structural insights that enhance our comprehension of the mechanisms underlying disintegrin functionality.

The Brazilian Atlantic Bushmaster Lachesis (Linnaeus, 1766) Mitogenome With Insights On Snake Evolution And Divergence (Serpentes: Viperidae: Crotalinae)

This study presents the first complete mitogenome of the Brazilian Atlantic bushmaster Lachesis with insights into snake evolution. The total length was 17,177 bp, consisting of 13 PCGs, 22 tRNAs, two rRNAs and a duplicate control region (CRs). Almost all genes were encoded by the heavy-strand, except for the ND6 gene and eight tRNAs (tRNA-Gln, Ala, Asn, Cys, Tyr, Ser[TGA anticodon], Glu, Pro). Only ATG, ATA, and ATC were starting codons for protein-coding sequences. Stop codons mainly were TAA, AGA, AGG, and TAG; whereas ND1, ND3, and CYTB terminated with incomplete stop codons. Phylogeny retrieved Lachesis within the Crotalinae as the sister group of Agkistrodon; and the Lachesis+Agkistrodon clade as the sister group of (Sistrurus+Crotalus)+Bothrops. The tree supports Crotalinae, Viperinae, and Azemiopinae in the Viperidae family, being sister taxa of Colubridae+(Elapidae+Psammophiidae). The mean genetic distance across 15 snake families and 57 nucleotide sequences was 0.37. The overall mean value of genetic distance across the Crotalinae was 0.23, with Lachesis muta exhibiting the shortest distance of 0.2 with Agkistrodon piscivorus, Protobothrops dabieshanensis and P. flavoviridis and the greatest 0.25 with Gloydius blomhoffii, Trimeresurus albolabris, S. miliarius, and Deinagkistrodon acutus. The complete Atlantic L. muta mitogenome presented herein is only the third annotated mitogenome from more than 430 described Brazilian snake species.

Proteomic Analysis of HCC-1954 and MCF-7 Cell Lines Highlights Crosstalk between αv and β1 Integrins, E-Cadherin and HER-2

Overexpression of human epidermal growth factor receptor-2 (HER-2) occurs in 20% of all breast cancer subtypes, especially those that present the worst prognostic outcome through a very invasive and aggressive tumour. HCC-1954 (HER-2+) is a highly invasive, metastatic cell line, whereas MCF-7 is mildly aggressive and non-invasive. We investigated membrane proteins from both cell lines that could have a pivotal biological significance in metastasis. Membrane protein enrichment for HCC-1954 and MCF-7 proteomic analysis was performed. The samples were analysed and quantified by mass spectrometry. High abundance membrane proteins were confirmed by Western blot, immunofluorescence, and flow cytometry. Protein interaction prediction and correlations with the Cancer Genome Atlas (TCGA) patient data were conducted by bioinformatic analysis. In addition, β1 integrin expression was analysed by Western blot in cells upon trastuzumab treatment. The comparison between HCC-1954 and MCF-7 membrane-enriched proteins revealed that proteins involved in cytoskeleton organisation, such as HER-2, αv and β1 integrins, E-cadherin, and CD166 were more abundant in HCC-1954. β1 integrin membrane expression was higher in the HCC-1954 cell line resistant after trastuzumab treatment. TCGA data analysis showed a trend toward a positive correlation between HER-2 and β1 integrin in HER-2+ breast cancer patients. Differences in protein profile and abundance reflected distinctive capabilities for aggressiveness and invasiveness between HCC-1954 and MCF-7 cell line phenotypes. The higher membrane β1 integrin expression after trastuzumab treatment in the HCC-1954 cell line emphasised the need for investigating the contribution of β1 integrin modulation and its effect on the mechanism of trastuzumab resistance.

Structure-Function Relationship of the Disintegrin Family: Sequence Signature and Integrin Interaction

Disintegrins are small cysteine-rich proteins found in a variety of snake venom. These proteins selectively modulate integrin function, heterodimeric receptors involved in cell-cell and cell-matrix interaction that are widely studied as therapeutic targets. Snake venom disintegrins emerged from the snake venom metalloproteinase and are classified according to the sequence size and number of disulfide bonds. Evolutive structure and function diversification of disintegrin family involves a stepwise decrease in the polypeptide chain, loss of cysteine residues, and selectivity. Since the structure elucidation of echistatin, the description of the structural properties of disintegrins has allowed the investigation of the mechanisms involved in integrin-cell-extracellular matrix interaction. This review provides an analysis of the structures of all family groups enabling the description of an expanded classification of the disintegrin family in seven groups. Each group presents a particular disulfide pattern and sequence signatures, facilitating the identification of new disintegrins. The classification was based on the disintegrin-like domain of the human metalloproteinase (ADAM-10). We also present the sequence and structural signatures important for disintegrin-integrin interaction, unveiling the relationship between the structure and function of these proteins.

Polyclonal F(ab')2 fragments of equine antibodies raised against the spike protein neutralize SARS-CoV-2 variants with high potency

We used the recombinant trimeric spike (S) glycoprotein in the prefusion conformation to immunize horses for the production of hyperimmune globulins against SARS-CoV-2. Serum antibody titers measured by ELISA were above 1:106, and the neutralizing antibody titer against authentic virus (WT) was 1:14,604 (average PRNT90). Plasma from immunized animals was pepsin digested to remove the Fc portion and purified, yielding an F(ab')2 preparation with PRNT90 titers 150-fold higher than the neutralizing titers in human convalescent plasma. Challenge studies were carried out in hamsters and showed the in vivo ability of equine F(ab')2 to reduce viral load in the pulmonary tissues and significant clinical improvement determined by weight gain. The neutralization curve by F(ab')2 was similar against the WT and P.2 variants, but displaced to higher concentrations by 0.39 log units against the P.1 (Gamma) variant. These results support the possibility of using equine F(ab')2 preparation for the clinical treatment of COVID patients.

Chalcones identify cTXNPx as a potential antileishmanial drug target

With current drug treatments failing due to toxicity, low efficacy and resistance; leishmaniasis is a major global health challenge that desperately needs new validated drug targets. Inspired by activity of the natural chalcone 2’,6’-dihydroxy-4’-methoxychalcone (DMC), the nitro-analogue, 3-nitro-2’,4’,6’- trimethoxychalcone (NAT22, 1c) was identified as potent broad spectrum antileishmanial drug lead. Structural modification provided an alkyne containing chemical probe that labelled a protein within the parasite that was confirmed as cytosolic tryparedoxin peroxidase (cTXNPx). Crucially, labelling is observed in both promastigote and intramacrophage amastigote life forms, with no evidence of host macrophage toxicity. Incubation of the chalcone in the parasite leads to ROS accumulation and parasite death. Deletion of cTXNPx, by CRISPR-Cas9, dramatically impacts upon the parasite phenotype and reduces the antileishmanial activity of the chalcone analogue. Molecular docking studies with a homology model of in-silico cTXNPx suggest that the chalcone is able to bind in the putative active site hindering access to the crucial cysteine residue. Collectively, this work identifies cTXNPx as an important target for antileishmanial chalcones.

Leishmaniasis is an insect vector-borne parasitic disease. With >350 million people world wide considered at risk, 12 million people currently infected and an economic cost that can be estimated in terms of >3.3 million working life years lost, leishmaniasis is a major global health challenge. The disease is of particular importance in Brazil. Current treatment of leishmaniasis is difficult requiring a long, costly course of drug treatment using old drugs with poor safety indications requiring close medical supervision. Moreover, resistance to current antileishmanials is growing, emphasising a major need for new drug targets. In earlier work we had identified a naturally inspired chalcone which had promising antileishmanial activity but with no known mode of action. In this work we use an analogue of this molecule as an activity based probe to identify a protein target of the chalcone. This protein, cTXNPx, has a major role in protecting the parasite against attack by reactive oxygen species in the host cell. By inhibiting this protein the parasite can no longer survive in the host. Collectively this work validates cTXNPx as a drug target with the chalcone as a lead structure for future drug discovery programmes.

Evaluation of the Enzymatic Arsenal Secreted by Myceliophthora thermophila During Growth on Sugarcane Bagasse With a Focus on LPMOs

The high demand for energy and the increase of the greenhouse effect propel the necessity to develop new technologies to efficiently deconstruct the lignocellulosic materials into sugars monomers. Sugarcane bagasse is a rich polysaccharide residue from sugar and alcohol industries. The thermophilic fungus Myceliophthora thermophila (syn. Sporotrichum thermophilum) is an interesting model to study the enzymatic degradation of biomass. The genome of M. thermophila encodes an extensive repertoire of cellulolytic enzymes including 23 lytic polysaccharide monooxygenases (LPMOs) from the Auxiliary Activity family 9 (AA9), which are known to oxidatively cleave the β-1,4 bonds and boost the cellulose conversion in a biorefinery context. To achieve a deeper understanding of the enzymatic capabilities of M. thermophila on sugarcane bagasse, we pretreated this lignocellulosic residue with different methods leading to solids with various cellulose/hemicellulose/lignin proportions and grew M. thermophila on these substrates. The secreted proteins were analyzed using proteomics taking advantage of two mass spectrometry methodologies. This approach unraveled the secretion of many CAZymes belonging to the Glycosyl Hydrolase (GH) and AA classes including several LPMOs that may contribute to the biomass degradation observed during fungal growth. Two AA9 LPMOs, called MtLPMO9B and MtLPMO9H, were selected from secretomic data and enzymatically characterized. Although MtLPMO9B and MtLPMO9H were both active on cellulose, they differed in terms of optimum temperatures and regioselectivity releasing either C1 or C1-C4 oxidized oligosaccharides, respectively. LPMO activities were also measured on sugarcane bagasse substrates with different levels of complexity. The boosting effect of these LPMOs on bagasse sugarcane saccharification by a Trichoderma reesei commercial cocktail was also observed. The partially delignified bagasse was the best substrate considering the oxidized oligosaccharides released and the acid treated bagasse was the best one in terms of saccharification boost.

Potent neutralizing equine antibodies raised against recombinant SARS-CoV-2 spike protein for COVID-19 passive immunization therapy.. [PMID: 0 DOI: 10.1101/2020.08.17.254375]

We used the trimeric spike (S) glycoprotein (residues 1-1208) in the prefusion conformation to immunize horses for production of hyperimmune globulins against SARS-CoV-2. Serum antibody titers measured by anti-spike ELISA were above 1:1,000,000, and neutralizing antibody titer was 1:14,604 (average PRNT90), which is 140-fold higher than the average neutralizing titer of plasma from three convalescent COVID-19 patients analyzed for comparison. Using the same technology routinely used for industrial production of other horse hyperimmune products, plasma from immunized animals was pepsin digested to remove the Fc portion and purified, yielding a F(ab’)2 preparation with PRNT90 titers 150-fold higher than the neutralizing titers in human convalescent plasma. Repeating the hyperimmunization in a second group of horses confirmed the very high neutralizing titers in serum and in a GMP clinical F(ab’)2 lot. Virus-neutralizing activity in samples from mice that received the F(ab’)2 preparation was detected even three days after injection, indicating an appropriate half-life for therapeutic intervention. These results supported the design of a clinical trial (identifier NCT04573855) to evaluate safety and efficacy of this horse F(ab’)2 preparation.

Polysaccharide composition of an anticoagulant fraction from the aqueous extract of Marsypianthes chamaedrys (Lamiaceae)

Marsypianthes chamaedrys (Lamiaceae) is a medicinal plant popularly used against envenomation by snakebite. Pharmacological studies have shown that extracts of M. chamaedrys have antiophidic, anti-inflammatory and anticoagulant properties, supporting the ethnopharmacological use. In this study, an aqueous extract of aerial parts of M. chamaedrys showed anticoagulant activity in the activated partial thromboplastin time assay (0.54 IU/mg). The bioassay-guided fractionation using ethanol precipitation and gel filtration chromatography on Sephadex G-50 and Sephadex G-25 resulted in a water-soluble fraction with increased anticoagulant activity (Fraction F2-A; 2.94 IU/mg). A positive correlation was found between the amount of uronic acids and the anticoagulant potential of the active samples. Chemical and spectroscopic analyses indicated that F2-A contained homogalacturonan, type I rhamnogalacturonan, type II arabinogalactan and α-glucan. UV and FT-IR spectra indicated the possible presence of ferulic acid. Pectic polysaccharides and type II arabinogalactans may be contributing to the anticoagulant activity of the aqueous extract of M. chamaedrys in the APTT assay.

Protein Profile of Blood Monocytes is Altered in HTLV-1 Infected Patients: Implications for HAM/TSP Disease

Human T-cell lymphotropic virus type-1 (HTLV-1) is the etiological agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The endothelial breakdown and migration of leukocytes, including monocytes, to the spinal cord are involved in HAM/TSP development. Monocytes from HTLV-1-infected individuals exhibit important functional differences when compared to cells from uninfected donors. Using proteomic shot gun strategy, performed by nanoACQUITY-UPLC system, we analyzed monocytes isolated from peripheral blood of asymptomatic carriers (AC), HAM/TSP and uninfected individuals. 534 proteins were identified among which 376 were quantified by ExpressionE software. Our study revealed a panel of changes in protein expression linked to HTLV-1 infection. Upregulation of heat shock proteins and downregulation of canonical histone expression were observed in monocytes from HTLV-1-infected patients. Moreover, expression of cytoskeleton proteins was increased in monocytes from HTLV-1-infected patients, mainly in those from HAM/TSP, which was confirmed by flow cytometry and fluorescence microscopy. Importantly, functional assays demonstrated that monocytes from HAM/TSP patients present higher ability for adhesion and transmigration thought endothelium than those from AC and uninfected individuals. The major changes on monocyte protein profile were detected in HAM/TSP patients, suggesting that these alterations exert a relevant role in the establishment of HAM/TSP.

Binding targets of termiticidal lectins from the bark and leaf of Myracrodruon urundeuva in the gut of Nasutitermes corniger workers

BACKGROUND

Lectins, carbohydrate-binding proteins, from the bark (MuBL) and leaf (MuLL) of Myracrodruon urundeuva are termiticidal agents against Nasutitermes corniger workers and have been shown to induce oxidative stress and cell death in the midgut of these insects. In this study, we investigated the binding targets of MuBL and MuLL in the gut of N. corniger workers by determining the effects of these lectins on the activity of digestive enzymes. In addition, we used mass spectrometry to identify peptides from gut proteins that adsorbed to MuBL-Sepharose and MuLL-Sepharose columns.

RESULTS

Exoglucanase activity was neutralized in the presence of MuBL and stimulated by MuLL. α-l-Arabinofuranosidase activity was not affected by MuBL but was inhibited by MuLL. Both lectins stimulated α-amylase activity and inhibited protease and trypsin-like activities. Peptides with homology to apolipophorin, trypsin-like enzyme, and ABC transporter substrate-binding protein were detected from proteins that adsorbed to MuBL-Sepharose, while peptides from proteins that bound to MuLL-Sepharose shared homology with apolipophorin.

CONCLUSION

This study revealed that digestive enzymes and transport proteins found in worker guts can be recognized by MuBL and MuLL. Thus, the mechanism of their termiticidal activity may involve changes in the digestion and absorption of nutrients. © 2018 Society of Chemical Industry.

The antithrombotic and haemostatic effects of LASSBio-752: a synthetic, orally active compound in an arterial and venous thrombosis model in rats

OBJECTIVES

In this work, we further investigated the effect of the compound LASSBio-752 in thrombosis models in rats.

METHODS

Arterial and venous thrombosis model, ex-vivo recalcification time and aPTT and PT.

KEY FINDINGS

In the venous thrombosis model, oral administration of LASSBio-752 [48.2 mg (100 μmol)/kg] one hour before the thrombus induction decreased thrombus weight by 37 ± 0.2%. Interestingly, the antithrombotic action of this compound [48.2 mg (100 μmol)/kg] occurred at 87.5 ± 2.1% of inhibition after 24 h of administration and showed a lasting activity. When tested on the arterial thrombosis model, after a 1-h interval, there was already an increase in time to total occlusion of 34 ± 2.4 min, but the greatest effect was observed at intervals between 6 and 15 h of administration, when no occlusion of the artery was observed. The antithrombotic effect was reduced after 24 h when the occlusion time was 23.8 ± 2.3 min, close to that of the control, 17.6 ± 2.0 min. We also observed that bleeding was not excessive in any of the intervals tested.

CONCLUSIONS

Our results indicate that compound LASSBio-752 is a potential candidate for utilization in the treatment of thromboembolic diseases.

Metaproteomics reveals metabolic transitions between healthy and diseased stony coral Mussismilia braziliensis

Infectious diseases such as white plague syndrome (WPS) and black band disease (BBD) have caused massive coral loss worldwide. We performed a metaproteomic study on the Abrolhos coral Mussismilia braziliensis to define the types of proteins expressed in healthy corals compared to WPS- and BBD-affected corals. A total of 6363 MS/MS spectra were identified as 361 different proteins. Healthy corals had a set of proteins that may be considered markers of holobiont homoeostasis, including tubulin, histone, Rab family, ribosomal, peridinin-chlorophyll a-binding protein, F0F1-type ATP synthase, alpha-iG protein, calmodulin and ADP-ribosylation factor. Cnidaria proteins found in healthy M. braziliensis were associated with Cnidaria-Symbiodinium endosymbiosis and included chaperones (hsp70, hsp90 and calreticulin), structural and membrane modelling proteins (actin) and proteins with functions related to intracellular vesicular traffic (Rab7 and ADP-ribosylation factor 1) and signal transduction (14-3-3 protein and calmodulin). WPS resulted in a clear shift in the predominance of proteins, from those related to aerobic nitrogen-fixing bacteria (i.e. Rhizobiales, Sphingomonadales and Actinomycetales) in healthy corals to those produced by facultative/anaerobic sulphate-reducing bacteria (i.e. Enterobacteriales, Alteromonadales, Clostridiales and Bacteroidetes) in WPS corals. BBD corals developed a diverse community dominated by cyanobacteria and sulphur cycle bacteria. Hsp60, hsp90 and adenosylhomocysteinase proteins were produced mainly by cyanobacteria in BBD corals, which is consistent with elevated oxidative stress in hydrogen sulphide- and cyanotoxin-rich environments. This study demonstrates the usefulness of metaproteomics for gaining better comprehension of coral metabolic status in health and disease, especially in reef systems such as the Abrolhos that are suffering from the increase in global and local threatening events.

A proteomic approach to compare saliva from individuals with and without oral leukoplakia

BACKGROUND

Oral leukoplakia is the most common potentially malignant disorder in the oral cavity and can precede carcinoma. This study aimed to identify possible oral leukoplakia salivary biomarkers.

METHODS

Unstimulated saliva was collected from participants and protein concentration was determined. Proteins were then precipitated with cold acetone and separated using 2DE over a pH range of 3-10. Spot demarcation and matching were performed and protein identification was done through MS analysis. Oral leukoplakia tissues were submitted to immunohistochemistry analysis for keratin 10 (CK10). A complementary analysis of oral leukoplakias that were not included previously was performed in addition.

RESULTS

226±10 spots were identified in oral leukoplakia 2DE gels, and 262±12 spots were identified in volunteers. Twenty-two spots were highly abundant in oral leukoplakias or not detected in the control group, such as apolipoprotein A1, alpha amylase, cystatins, keratin 10, and lysozyme precursor. All were identified. All oral leukoplakia cases were immunopositive for CK10, mainly in the superficial epithelial layers.

CONCLUSIONS

The 2DE salivary protein profiles of individuals with and without oral leukoplakia were observably different. CK10 appears to be an interesting protein and should be further studied in oral carcinogenesis.

SIGNIFICANCE

MS-based proteomics enables large-scale analysis of proteins. Proteomics can provide detailed descriptions of proteomes of cells and tissues, including body fluids, and appears as a powerful tool to study human disorders. Saliva is readily accessible through non invasive collection and can mirror diverse disease states. Saliva from both diseased and healthy subjects can be analyzed through 2DE and differences between groups could be found. Routine immunohistochemistry analysis confirmed one of these findings, with CK10 being positive tissues from individuals with oral leukoplakia. Therefore, the present study allows insights into development of an important potential oral cancer precursor, named oral leukoplakia. However, the results can be extrapolated and tested in other precancer states, such as proliferative verrucous leukoplakia, patients at risk of oral cancer due to lifestyle behavior and/or cancer history in the family or even those who are under surveillance after a treated primary oral cancer.

Proteomics of cell-cell interactions in health and disease

The mechanisms of cell-cell communications are now under intense study by proteomic approaches. Proteomics has unraveled changes in protein profiling as the result of cell interactions mediated by ligand/receptor, hormones, soluble factors, and the content of extracellular vesicles. Besides being a brief overview of the main and profitable methodologies now available (evaluating theory behind the methods, their usefulness, and pitfalls), this review focuses on-from a proteome perspective-some signaling pathways and post-translational modifications (PTMs), which are essential for understanding ischemic lesions and their recovery in two vital organs in mammals, the heart, and the kidney. Knowledge of misdirection of the proteome during tissue recovery, such as represented by the convergence between fibrosis and cancer, emerges as an important tool in prognosis. Proteomics of cell-cell interaction is also especially useful for understanding how stem cells interact in injured tissues, anticipating clues for rational therapeutic interventions. In the effervescent field of induced pluripotency and cell reprogramming, proteomic studies have shown what proteins from specialized cells contribute to the recovery of infarcted tissues. Overall, we conclude that proteomics is at the forefront in helping us to understand the mechanisms that underpin prevalent pathological processes.

Combined venomics, venom gland transcriptomics, bioactivities, and antivenomics of two Bothrops jararaca populations from geographic isolated regions within the Brazilian Atlantic rainforest

Bothrops jararaca is a slender and semi-arboreal medically relevant pit viper species endemic to tropical and subtropical forests in southern Brazil, Paraguay, and northern Argentina (Misiones). Within its geographic range, it is often abundant and is an important cause of snakebite. Although no subspecies are currently recognized, geographic analyses have revealed the existence of two well-supported B. jararaca clades that diverged during the Pliocene ~3.8Mya and currently display a southeastern (SE) and a southern (S) Atlantic rainforest (Mata Atlântica) distribution. The spectrum, geographic variability, and ontogenetic changes of the venom proteomes of snakes from these two B. jararaca phylogroups were investigated applying a combined venom gland transcriptomic and venomic analysis. Comparisons of the venom proteomes and transcriptomes of B. jararaca from the SE and S geographic regions revealed notable interpopulational variability that may be due to the different levels of population-specific transcriptional regulation, including, in the case of the southern population, a marked ontogenetic venom compositional change involving the upregulation of the myotoxic PLA2 homolog, bothropstoxin-I. This population-specific marker can be used to estimate the proportion of venom from the southern population present in the B. jararaca venom pool used for the Brazilian soro antibotrópico (SAB) antivenom production. On the other hand, the southeastern population-specific D49-PLA2 molecules, BinTX-I and BinTX-II, lend support to the notion that the mainland ancestor of Bothrops insularis was originated within the same population that gave rise to the current SE B. jararaca phylogroup, and that this insular species endemic to Queimada Grande Island (Brazil) expresses a pedomorphic venom phenotype. Mirroring their compositional divergence, the two geographic B. jararaca venom pools showed distinct bioactivity profiles. However, the SAB antivenom manufactured in Vital Brazil Institute neutralized the lethal effect of both venoms to a similar extent. In addition, immobilized SAB antivenom immunocaptured most of the venom components of the venoms of both B. jararaca populations, but did not show immunoreactivity against vasoactive peptides. The Costa Rican bothropic-crotalic-lachesic (BCL) antivenom showed the same lack of reactivity against vasoactive peptides but, in addition, was less efficient immunocapturing PI- and PIII-SVMPs from the SE venom, and bothropstoxin-I, a CRISP molecule, and a D49-PLA2 from the venom of the southern B. jararaca phylogroup. The remarkable paraspecificity exhibited by the Brazilian and the Costa Rican antivenoms indicates large immunoreactive epitope conservation across the natural history of Bothrops, a genus that has its roots in the middle Miocene. This article is part of a Special Issue entitled: Omics Evolutionary Ecolog.

Isoforms of Hsp70-binding human LDL in adult Schistosoma mansoni worms

Schistosoma mansoni is one of the most common parasites infecting humans. They are well adapted to the host, and this parasite's longevity is a consequence of effective escape from the host immune system. In the blood circulation, lipoproteins not only help to conceal the worm from attack by host antibodies but also act as a source of lipids for S. mansoni. Previous SEM studies showed that the low-density lipoprotein (LDL) particles present on the surface of adult S. mansoni worms decreased in size when the incubation time increased. In this study, immunocytochemical and proteomic analyses were used to locate and identify S. mansoni binding proteins to human plasma LDL. Ultrathin sections of adult worms were cut transversely from the anterior, medial and posterior regions of the parasite. Immunocytochemical experiments revealed particles of gold in the tegument, muscle region and spine in male worms and around vitelline cells in females. Immunoblotting and 2D-electrophoresis using incubations with human serum, anti-LDL antibodies and anti-chicken IgG peroxidase conjugate were performed to identify LDL-binding proteins in S. mansoni. Analysis of the binding proteins using LC-MS identified two isoforms of the Hsp70 chaperone in S. mansoni. Hsp70 is involved in the interaction with apoB in the cytoplasm and its transport to the endoplasmic reticulum. However, further studies are needed to clarify the functional role of Hsp70 in S. mansoni, mainly related to the interaction with human LDL.

Functional variability of snake venom metalloproteinases: adaptive advantages in targeting different prey and implications for human envenomation

Snake venom metalloproteinases (SVMPs) are major components in most viperid venoms that induce disturbances in the hemostatic system and tissues of animals envenomated by snakes. These disturbances are involved in human pathology of snake bites and appear to be essential for the capture and digestion of snake's prey and avoidance of predators. SVMPs are a versatile family of venom toxins acting on different hemostatic targets which are present in venoms in distinct structural forms. However, the reason why a large number of different SVMPs are expressed in some venoms is still unclear. In this study, we evaluated the interference of five isolated SVMPs in blood coagulation of humans, birds and small rodents. P-III class SVMPs (fractions Ic, IIb and IIc) possess gelatinolytic and hemorrhagic activities, and, of these, two also show fibrinolytic activity. P-I class SVMPs (fractions IVa and IVb) are only fibrinolytic. P-III class SVMPs reduced clotting time of human plasma. Fraction IIc was characterized as prothrombin activator and fraction Ic as factor X activator. In the absence of Ca²⁺, a firm clot was observed in chicken blood samples with fractions Ic, IIb and partially with fraction IIc. In contrast, without Ca²⁺, only fraction IIc was able to induce a firm clot in rat blood. In conclusion, functionally distinct forms of SVMPs were found in B. neuwiedi venom that affect distinct mechanisms in the coagulation system of humans, birds and small rodents. Distinct SVMPs appear to be more specialized to rat or chicken blood, strengthening the current hypothesis that toxin diversity enhances the possibilities of the snakes for hunting different prey or evading different predators. This functional diversity also impacts the complexity of human envenoming since different hemostatic mechanisms will be targeted by SVMPs accounting for the complexity of the response of humans to venoms.

Molecular characterization of Rhodnius prolixus' embryonic cuticle

The embryonic cuticle (EC) of Rhodnius prolixus envelopes the entire body of the embryo during hatching and provides physical protection, allowing the embryo to pass through a narrow chorionic border. Most of the knowledge about the EC of insects is derived from studies on ultrastructure and secretion processes during embryonic development, and little is known about the molecular composition of this structure. We performed a comprehensive molecular characterization of the major components extracted from the EC of R. prolixus, and we discuss the role of the different molecules that were identified during the eclosion process. The results showed that, similar to the post-embryonic cuticles of insects, the EC of R. prolixus is primarily composed of carbohydrates (57%), lipids (19%), and proteins (8%). Considering only the carbohydrates, chitin is by far the major component (approximately 70%), and it is found primarily along the body of the EC. It is scarce or absent in its prolongations, which are composed of glycosaminoglycans. In addition to chitin, we also identified amino (15%), neutral (12%) and acidic (3%) carbohydrates in the EC of R. prolixus. In addition carbohydrates, we also identified neutral lipids (64.12%) and phospholipids (35.88%). Proteomic analysis detected 68 proteins (55 were identified and 13 are hypothetical proteins) using the sequences in the R. prolixus genome (http://www.vectorbase.org). Among these proteins, 8 out of 15 are associated with cuticle metabolism. These proteins are unequivocally cuticle proteins, and they have been described in other insects. Approximately 35% of the total proteins identified were classified as having a structural function. Chitin-binding protein, amino peptidase, amino acid oxidase, oxidoreductase, catalase and peroxidase are all proteins associated with cuticle metabolism. Proteins known to be cuticle constituents may be related to the function of the EC in assisting the insect during eclosion. To our knowledge, this is the first study to describe the global molecular composition of an EC in insects.

Four conventional soybean [Glycine max (L.) Merrill] seeds exhibit different protein profiles as revealed by proteomic analysis

Soybeans have several functional properties due to their composition and may exert beneficial health effects that are attributed to proteins and their derivative peptides. The present study aimed to analyze the protein profiles of four new conventional soybean seeds (BRS 257, BRS 258, BRS 267, and Embrapa 48) with the use of proteomic tools. Two-dimensional (2D) and one-dimensional (1D) gel electrophoreses were performed, followed by MALDI-TOF/TOF and ESI-Q-TOF mass spectrometry analyses, respectively. These two different experimental approaches allowed the identification of 117 proteins from 1D gels and 46 differentially expressed protein spots in 2D gels. BRS 267 showed the greatest diversity of identified spots in the 2D gel analyses. In the 1D gels, the major groups were storage (25-40%) and lipid metabolism (11-25%) proteins. The differences in protein composition between cultivars could indicate functional and nutritional differences and could direct the development of new cultivars.

Feather keratin hydrolysates obtained from microbial keratinases: effect on hair fiber

Background

Hair is composed mainly of keratin protein and a small amount of lipid. Protein hydrolysates, in particular those with low molecular weight distribution have been known to protect hair against chemical and environmental damage. Many types of protein hydrolysates from plants and animals have been used in hair and personal care such as keratin hydrolysates obtained from nails, horns and wool. Most of these hydrolysates are obtained by chemical hydrolysis and hydrothermal methods, but recently hydrolyzed hair keratin, feather keratin peptides, and feather meal peptides have been obtained by enzymatic hydrolysis using Bacillus spp in submerged fermentation.

Results

Keratin peptides were obtained by enzymatic hydrolysis of keratinases using Bacillus subtilis AMR. The microorganism was grown on a feather medium, pH 8.0 (1% feathers) and supplemented with 0.01% of yeast extract, for 5 days, at 28°C with agitation. The supernatant containing the hydrolysates was colleted by centrifugation and ultra filtered in an AMICON system using nano–membranes (Millipore – YC05). The Proteins and peptides were analyzed using HPTLC and MALDI-TOF-MS. Commercial preparations of keratin hydrolysates were used as a comparative standard. After five days the feather had been degraded (90-95%) by the peptidases and keratinases of the microorganism. MALDI-TOF mass spectrometry showed multiple peaks that correspond to peptides in the range of 800 to 1079 Daltons and the commercial hydrolysate was in the range of 900 to 1400 Da. HPTLC showed lower molecular mass peptides and amino acids in the enzymatic hydrolysate when compared with the commercial hydrolysate . A mild shampoo and a rinse off conditioner were formulated with the enzymatic hydrolysate and applied to hair fibers to evaluate the hydration, with and without heat, using a Corneometer® CM 825. The hydration was more efficient with heat, suggesting a more complete incorporation of hydrolysates into the fibers. Scanning Electron Microscopy showed deposits of organic matter in the junction of the cuticles that probably collaborates to the sealing of the cuticles, increasing the brightness and softness.

Conclusions

These results show that the enzymatic method to produce keratin peptides for hair care products is an attractive and eco- friendly method with a great potential in the cosmetic industry.

The molecular and structural characterization of two vitellogenins from the free-living nematode Oscheius tipulae

This paper describes the purification of yolk proteins, which are important for the reproduction of egg-laying animals, and the structural characterization of two vitellogenins, VT1 and OTI-VIT-6, of the nematode Oscheius tipulae. O. tipulae is an alternative model organism to its relative, the widely used Caenorhabditis elegans, and is a good model to understand reproduction in insect parasitic nematodes of the genus Heterorhabditis. The native purified O. tipulae vitellogenin is composed of three polypeptides (VT1, VT2 and VT3), whereas in C. elegans, vitellogenin is composed of four polypeptides. The gene (Oti-vit-1) encoding yolk polypeptide VT1 has been recently identified in the genome of O. tipulae. Immunoblotting and N-terminal sequencing confirmed that VT1 is indeed coded by Oti-vit-1. Utilizing the same experimental approaches, we showed that the polypeptides VT2 and VT3 are derived from the proteolytic processing of the C- and N-terminal portions of the precursor OTI-VIT-6, respectively. We also showed that the recombinant polypeptide (P40), corresponding to the N-terminal sequence of OTI-VIT-6, preferentially interacts with a 100-kDa polypeptide found in adult worm extracts, as we have previously shown for the native vitellins of O. tipulae. Using the putative nematode vitellogenin amino acid sequences available in the UniProtKB database, we constructed a phylogenetic tree and showed that the O. tipulae vitellogenins characterized in this study are orthologous to those of the Caenorhabditis spp. Together, these results represent the first structural and functional comparative study of nematode yolk proteins outside the Caenorhabditis genus and provide insight into the evolution of these lipoproteins within the Nematode Phylum.

Label-free quantitative proteomics reveals differentially regulated proteins in the latex of sticky diseased Carica papaya L. plants

Papaya meleira virus (PMeV) is so far the only described laticifer-infecting virus, the causal agent of papaya (Carica papaya L.) sticky disease. The effects of PMeV on the laticifers' regulatory network were addressed here through the proteomic analysis of papaya latex. Using both 1-DE- and 1D-LC-ESI-MS/MS, 160 unique papaya latex proteins were identified, representing 122 new proteins in the latex of this plant. Quantitative analysis by normalized spectral counting revealed 10 down-regulated proteins in the latex of diseased plants, 9 cysteine proteases (chymopapain) and 1 latex serine proteinase inhibitor. A repression of papaya latex proteolytic activity during PMeV infection was hypothesized. This was further confirmed by enzymatic assays that showed a reduction of cysteine-protease-associated proteolytic activity in the diseased papaya latex. These findings are discussed in the context of plant responses against pathogens and may greatly contribute to understand the roles of laticifers in plant stress responses.

Phenolic Chemical Composition of Petroselinum Crispum Extract and Its Effect on Haemostasis

From the aqueous extract (Pc) of Petroselinum crispum (Mill) flat leaves specimens were isolated and identified the flavonoids apigenin (1), apigenin-7- O-glucoside or cosmosiin (2), apigenin-7- O-apiosyl-(1→2)- O-glucoside or apiin (3) and the coumarin 2″,3″-dihydroxy-furanocoumarin or oxypeucedanin hydrate (4). The inhibitory activity toward clotting formation and platelet aggregation was assessed for Pc flavonoids (1) and (2), and the coumarin (4). Pc showed no inhibition on clotting activity when compared with the control. On the other hand, a strong antiplatelet aggregation activity was observed for Pc (IC50 = 1.81 mg/mL), apigenin (IC50 = 0.036 mg/mL) and cosmosiin (IC50 = 0.18 mg/mL). In all cases ADP was used as inductor of platelet aggregation. Our results showed that Pc, apigenin and cosmosiin interfere on haemostasis inhibiting platelet aggregation. To the best of our knowledge this is the first report for the cosmosiin antiplatelet aggregation in vitro activity.

Analysis of the salivary proteome in gingivitis patients

BACKGROUND AND OBJECTIVE

Gingivitis is a disease that is characterized by inflammation of the gingival tissue, which can progress to periodontitis and tooth loss. Although many studies have attempted to identify salivary proteins that are associated with the disease, this is the first study to use a proteomic approach to analyze and compare the proteomic profile of whole saliva from gingivitis patients and healthy controls.

MATERIAL AND METHOD

To analyze the saliva proteome, two-dimensional gel electrophoresis and liquid chromatography were used, followed by mass spectrometry.

RESULTS

The analyses showed that gingival inflammation was associated with increased amounts of blood proteins (serum albumin and hemoglobin), immunoglobulin peptides and keratins. In the control group, salivary cystatins, which were detected using capillary Liquid Chromatography on line to electrospray ionization Quadrupole Time-of-flight mass spectrometry, appeared to be more abundant.

CONCLUSION

This approach provides novel insight into profiles of the salivary proteome during gingival inflammation, which may contribute to improvements in diagnosis.

Production, purification and characterization of a thermostable β-1,3-glucanase (laminarinase) produced by Moniliophthora perniciosa

The enzyme glucanase from Moniliophthora perniciosa was produced in liquid medium and purified from the culture supernatant. A multivariate statistical approach (Response Surface Methodology - RSM) was employed to evaluate the effect of variables, including inducer (yeast extract) and fermentation time, on secreted glucanase activities M. perniciosa detected in the culture medium. The crude enzyme present in the supernatant was purified in two steps: precipitation with ammonium sulfate (70%) and gel filtration chromatography on Sephacryl S-200. The best inducer and fermentation time for glucanase activities were 5.9 g L-1 and 13 days, respectively. The results revealed three different isoforms (GLUI, GLUII and GLUIII) with purification factors of 4.33, 1.86 and 3.03, respectively. The partially purified enzymatic extract showed an optimum pH of 5.0 and an optimum temperature of 40°C. The enzymatic activity increased in the presence of KCl at all concentrations studied. The glucanase activity was highest in the presence of 0.2 M NaCl. The enzyme showed high thermal stability, losing only 10.20% of its specific activity after 40 minutes of incubation at 90°C. A purified enzyme with relatively good thermostability that is stable at low pH might be used in future industrial applications.

Effect of Moringa oleifera lectin on development and mortality of Aedes aegypti larvae

Aedes aegypti larvae have developed tolerance to many insecticides used for mosquito control. Moringa oleifera seeds contain a water-soluble lectin (WSMoL) and this paper reports the effect of M. oleifera seed extracts (MoE(1-15)) and WSMoL on development and survival of A. aegypti larvae. WSMoL peptide from in-gel trypsin digestion is also described. MoE(1-15) showed hemagglutinating activity and WSMoL had similarity with flocculating proteins from M. oleifera seeds. MoE(1) and MoE(3) delayed larval development which stopped in the third instar (L3) in MoE(6) and MoE(15). Significant (p<0.0001) larval mortality was only detected in MoE(15). Native WSMoL showed larvicidal activity (LC(50) 0.197 mg mL(-1)) and heated lectin, without hemagglutinating activity, did not kill fourth instar (L4) larvae. Optical microscopy showed that live L4 from MoE(1) presented underlying epithelium, increased gut lumen and hypertrophic segments; dead L4 from WSMoL were absent of underlying epithelium, had increased gut lumen and hypertrophic segments. The presence of hemagglutinating activity in the extracts suggests that soluble lectin promotes the delay of larval development and mortality; furthermore, the absence of larvicidal activity in heat-denatured WSMoL strengthens the involvement of lectin in this activity mechanism.

Evaluation of sample preparation methods for the analysis of papaya leaf proteins through two-dimensional gel electrophoresis

INTRODUCTION

A variety of sample preparation protocols for plant proteomic analysis using two-dimensional gel electrophoresis (2-DE) have been reported. However, they usually have to be adapted and further optimised for the analysis of plant species not previously studied.

OBJECTIVE

This work aimed to evaluate different sample preparation protocols for analysing Carica papaya L. leaf proteins through 2-DE.

METHODOLOGY

Four sample preparation methods were tested: (1) phenol extraction and methanol-ammonium acetate precipitation; (2) no precipitation fractionation; and the traditional trichloroacetic acid-acetone precipitation either (3) with or (4) without protein fractionation. The samples were analysed for their compatibility with SDS-PAGE (1-DE) and 2-DE. Fifteen selected protein spots were trypsinised and analysed by matrix-assisted laser desorption/ionisation time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS), followed by a protein search using the NCBInr database to accurately identify all proteins.

RESULTS

Methods number 3 and 4 resulted in large quantities of protein with good 1-DE separation and were chosen for 2-DE analysis. However, only the TCA method without fractionation (no. 4) proved to be useful. Spot number and resolution advances were achieved, which included having an additional solubilisation step in the conventional TCA method. Moreover, most of the theoretical and experimental protein molecular weight and pI data had similar values, suggesting good focusing and, most importantly, limited protein degradation.

CONCLUSION

The described sample preparation method allows the proteomic analysis of papaya leaves by 2-DE and mass spectrometry (MALDI-TOF-MS/MS). The methods presented can be a starting point for the optimisation of sample preparation protocols for other plant species.

Engineering ecotin for identifying proteins with a trypsin fold

Ecotin is a bidentate, fold-specific inhibitor of mammalian serine-proteases produced by Escherichia coli. This molecule may be engineered to increase and/or change its affinity and specificity providing significant biotechnological potential. Since ecotin binds tightly to serine proteases of the trypsin fold, it may help to identify the role of these enzymes in different biological processes. In this work, we tested ecotin variants as an affinity purification reagent for identifying enzymes in samples of tumor progression and mammary gland involution. Initially, we used a commercial source of urokinase-type plasminogen activator (u-PA) that remained fully active after elution from an affinity column of the ecotin variant (M84R, M85R). We then successfully identified u-PA from more complex mixtures including lysates from a prostate cancer cell line and involuting mouse mammary glands. Interestingly, a membrane-type serine protease 1 was isolated from the Triton X-100-solubilized PC-3 cell lysates, and surprisingly, haptoglobin, a serine-protease homolog protein, was also identified in mammary gland lysates and in blood. Haptoglobin does not prevent ecotin inhibition of u-PA, but it may act as a carrier within blood when ecotin is used in vivo. Finally, this affinity purification matrix was also able to identify a thrombin-like enzyme from snake venom using an ecotin variant directed against thrombin. Overall, the ecotin variants acted as robust tools for the isolation and characterization of proteins with a trypsin fold. Thus, they may assist in the understanding of the role of these serine proteases and homologous proteins in different biological processes.

Integrin inhibitors from snake venom: exploring the relationship between the structure and activity of RGD-peptides

alphaIIbbeta3 is an integrin that is involved in platelet adhesion and aggregation. This receptor may be inhibited by cysteine-rich peptides known as disintegrins. We isolated two disintegrins from Bothrops jararaca venom called jarastatin and jararacin. We evaluated the structural characteristics and the effects on human platelet aggregation of these disintegrins. Inhibitory profiles were compared to six distinct peptides synthesized based on their RGD hairpin loop primary sequences. Both jarastatin and jararacin inhibited ADP and thrombin induction. Conversely, none of the cyclic peptides showed high-quality activity in assays induced by ADP or thrombin. We constructed homology models for all of these molecules, and theoretically evaluated their interaction with the alphaIIbbeta3 crystal structure using a molecular modeling approach. These results support the observations that the cyclic peptides had little effects, and also reinforce the observation that residues outside the disintegrin RGD sequence are required for interactions with receptor.

Synthesis and anti-platelet activity of novel arylsulfonate–acylhydrazone derivatives, designed as antithrombotic candidates

In this work, we describe a new class of promising anti-platelet drug candidates with significant antithrombotic activity in vivo. This new series of compounds was structurally planned by modification of known thrombin inhibitors based on the use of acylhydrazone subunit, as a nonpeptide scaffold, and variations at P1 moiety. Three different families of arylsulfonate-acylhydrazone derivatives were designed. The bioassays indicated the first class of derivatives represented by 4f (LASSBio-693) and 4j (LASSBio-743), which were active in inhibiting the platelet aggregation induced by thrombin. The second class represented by compounds 4e (LASSBio-774) and 4h (LASSBio-480) that selectively inhibit the platelet aggregation involving TXA(2) formation. Finally, the third class of derivatives was identified acting as a novel symbiotic agent able to inhibit the platelet aggregation induced by collagen or AA and by thrombin, represented by compounds 4b (LASSBio-694) and 4g (LASSBio-770).

Molecular characterization of BjussuSP-I, a new thrombin-like enzyme with procoagulant and kallikrein-like activity isolated from Bothrops jararacussu snake venom

A thrombin-like enzyme, named BjussuSP-I, isolated from Bothrops jararacussu snake venom, is an acidic single-chain glycoprotein with M(r)=61,000, pI approximately 3.8 and 6% sugar. BjussuSP-I shows high proteolytic activity upon synthetic substrates, such as S-2238 and S-2288. It also shows procoagulant and kallikrein-like activity, but is unable to act on platelets and plasmin. These activities are inhibited by specific inhibitors of this class of enzymes. The complete cDNA sequence of BjussuSP-I with 696bp encodes open reading frames of 232 amino acid residues, which conserve the common domains of thrombin-like serine proteases. BjussuSP-I shows a high structural homology with other thrombin-like enzymes from snake venoms where common amino acid residues are identified as those corresponding to the catalytic site and subsites S1, S2 and S3 already reported. In this study, we also demonstrated the importance of N-linked glycans to improve thrombin-like activity of BjussuSP-I toxin.

Suramin counteracts the haemostatic disturbances produced by Bothrops jararaca snake venom

Snakebite accidents produced by Bothrops jararaca typically results in haemostatic changes including pro- and anticoagulant disturbs as well as interference with platelets. Suramin is a hexasulfonated naphthylurea derivative that was recently characterized as a thrombin inhibitor (Monteiro et al., 2004. Suramin interaction with human alpha-thrombin: inhibitory effects and binding studies. Int. J. Biochem. Cell Biol. 36(10), 2077-2085). Here, we evaluated the ability of suramin to counteract some of the haemostatic disturbs produced by B. jararaca venom. In vitro assays showed that suramin inhibited venom-induced hydrolysis of a number of synthetic substrates: S-2238, S-2266, S-2302 and S-2288, being this ability more prominent towards the thrombin substrate S-2238 (IC(50)=4.3 microM). It was also observed that suramin impaired the fibrinogen clotting induced by B. jararaca venom (IC(50)=124 microM). Accordingly, increasing concentrations of suramin progressively delayed venom-induced plasma clotting, with complete inhibition attained at concentrations above 1.0 mM. In addition, the platelet-aggregating properties of B. jararaca venom were inhibited by suramin in a dose-dependent fashion (IC(50)=127 microM). Suramin showed no effect in the in vivo hemorrhagic effect of venom in mouse skin. The in vivo effect of suramin was further tested using a previously established venous thrombosis model in rats induced by intravenous administration of B. jararaca venom combined with stasis. Venom doses of 100 microg/kg produced 100% of thrombus incidence (10.6+/-1.7 mg). On the other hand, previous administration of suramin partially inhibited thrombus formation. Thus, 12.5 or 25 mg/kg of suramin decreased thrombus weight by 24% and 40%, respectively. Remarkably, co-administration of 3 microL/kg of antibothropic serum (which has no effect on thrombus formation) and 12.5 mg/kg of suramin decreased thrombus weight by 75%, suggesting a synergic effect. Altogether, we demonstrate here that suramin inhibits in vitro and in vivo haemostatic changes caused by B. jararaca venom. At this point, this drug could be of potential interest for association with conventional antiserum therapy.

Partial purification of tightly bound mitochondrial hexokinase from maize (Zea mays L.) root membranes

In mammals, hexokinase (HK) is strategically located at the outer membrane of mitochondria bound to the porin protein. The mitochondrial HK is a crucial modulator of apoptosis and reactive oxygen species generation. In plants, these properties related to HK are unknown. In order to better understand the physiological role of non-cytosolic hexokinase (NC-HK) in plants, we developed a purification strategy here described. Crude extract of 400 g of maize roots (230 mg protein) contained a specific activity of 0.042 micromol G6P min(-1) mg PTN(-1). After solubilization with detergent two fractions were obtained by DEAE column chromatography, NC-HK 1 (specific activity = 3.6 micromol G6P min(-1) mg PTN(-1) and protein recovered = 0.7 mg) and NC-HK 2. A major purification (yield = 500-fold) was obtained after passage of NC-HK 1 through the hydrophobic phenyl-Sepharose column. The total amount of protein and activity recovered were 0.04 and 18%, respectively. The NC-HK 1 binds to the hydrophobic phenyl-Sepharose matrix, as observed for rat brain HK. Mild chymotrypsin digestion did not affect adsorption of NC-HK 1 to the hydrophobic column as it does for rat HK I. In contrast to mammal mitochondrial HK, glucose-6-phosphate, clotrimazole or thiopental did not dissociate NC-HK from maize (Zea mays) or rice (Oryza sativa) mitochondrial membranes. These data show that the interaction between maize or rice NC-HK to mitochondria differs from that reported in mammals, where the mitochondrial enzyme can be displaced by modulators or pharmacological agents known to interfere with the enzyme binding properties with the mitochondrial porin protein.