Nucleotide sequence of cDNA for Acacia confusa trypsin inhibitor and implication of post-translation processing

Structure of a Kunitz-type potato cathepsin D inhibitor

Potato cathepsin D inhibitor (PDI) is a glycoprotein of 188 amino acids which can inhibit both the aspartic protease cathepsin D and the serine protease trypsin. Here we report the first X-ray structure of PDI at a resolution of 2.1 Å showing that PDI adopts a β-trefoil fold, which is typical of the Kunitz-family protease inhibitors, with the inhibitory loops protruding from the core. Possible reactive-site loops including one involving a unique disulphide and another involving a protruding 310 helix are identified and docking studies indicate the mode of action of this unusual bi-functional inhibitor.

Bioinsecticidal activity of a novel Kunitz trypsin inhibitor from Catanduva (Piptadenia moniliformis) seeds

The present study aims to provide new in vitro and in vivo biochemical information about a novel Kunitz trypsin inhibitor purified from Piptadenia moniliformis seeds. The purification process was performed using TCA precipitation, Trypsin-Sepharose and reversed-phase C18 HPLC chromatography. The inhibitor, named PmTKI, showed an apparent molecular mass of around 19 kDa, visualized by SDS-PAGE, which was confirmed by mass spectrometry MALDI-ToF demonstrating a monoisotopic mass of 19.296 Da. The inhibitor was in vitro active against trypsin, chymotrypsin and papain. Moreover, kinetic enzymatic studies were performed aiming to understand the inhibition mode of PmTKI, which competitively inhibits the target enzyme, presenting Ki values of 1.5 × 10(-8) and 3.0 × 10(-1) M against trypsin and chymotrypsin, respectively. Also, the inhibitory activity was assayed at different pH ranges, temperatures and reduction environments (DTT). The inhibitor was stable in all conditions maintaining an 80% residual activity. N-terminal sequence was obtained by Edman degradation and the primary sequence presented identity with members of Kunitz-type inhibitors from the same subfamily. Finally after biochemical characterization the inhibitory effect was evaluated in vitro on insect digestive enzymes from different orders, PmTKI demonstrated remarkable activity against enzymes from Anthonomus grandis (90%), Plodia interpuncptella (60%), and Ceratitis capitata (70%). Furthermore, in vivo bioinsecticidal assays of C. capitata larvae were also performed and the concentration of PmTKI (w/w) in an artificial diet required to LD50 and ED50 larvae were 0.37 and 0.3% respectively. In summary, data reported here shown the biotechnological potential of PmTKI for insect pest control.

Inhibitory effects of a Kunitz-type inhibitor from Pithecellobium dumosum (Benth) seeds against insect-pests' digestive proteinases

Pithecellobium dumosum is a tree belonging to the Mimosoideae subfamily that presents various previously characterized Kunitz-type inhibitors. The present study provides a novel Kunitz-trypsin inhibitor isoform purified from P. dumosum seeds. Purification procedure was performed by TCA precipitation followed by a trypsin-Sepharose chromatography and a further reversed-phase HPLC. Purified inhibitor (PdKI-4) showed enhanced inhibitory activity against bovine trypsin and chymotrypsin. Furthermore, PdKI-4 showed remarkable inhibitory activity against serine proteases from the coleopterans Callosobruchus maculatus and Zabrotes subfasciatus, and the lepidopterans Alabama argillacea and Telchin licus. However, PdKI-4 was unable to inhibit porcine pancreatic elastase, pineapple bromelain and Carica papaya papain. SDS-PAGE showed that PdKI-4 consisted of a single polypeptide chain with molecular mass of 21 kDa. Kinetic studies demonstrated that PdKI-4 is probably a competitive inhibitor with a Ki value of 5.7 × 10(-10) M for bovine trypsin. PdKI-4 also showed higher stability over a wide range of temperature (37-100 °C) and pH (2-12). N-termini sequence was obtained by Edman degradation showing higher identity with other Mimosoideae subfamily Kunitz-type inhibitor members. In summary, data here reported indicate the biotechnological potential of PdKI-4 for development of products against insect-pests.

A novel trypsin inhibitor from Peltophorum dubium seeds, with lectin-like properties, triggers rat lymphoma cell apoptosis

A trypsin inhibitor (PDTI) was isolated from Peltophorum dubium seeds by affinity chromatography on a thyroglobulin-agarose or a trypsin-agarose column. In both cases, SDS-PAGE showed two bands of M(r) 20,000 and 22,000, which could not be resolved. Their amino-terminal sequences were identical and similar to that of Kunitz-type soybean trypsin inhibitor (SBTI). Mass spectrometry analysis of tryptic digests of both bands showed 16 coincident peaks, suggesting that they are closely related proteins. The K(i)s for trypsin and chymotrypsin inhibitory activity of PDTI were 1.6 x 10(-7) and 1.3 x 10(-5)M, respectively. Lectin-like activity of PDTI and SBTI, detected by hemagglutination of rabbit erythrocytes, was inhibited by sialic acid-containing compounds. PDTI and SBTI caused apoptosis of Nb2 rat lymphoma cells, demonstrated by decrease of viability, DNA hypodiploidy, DNA fragmentation, and caspase-3-like activity. They had no effect on normal mouse splenocytes or lymphocytes, whereas they caused apoptosis of concanavalin A-stimulated mouse lymphocytes.

Primary structure and function analysis of the Abrus precatorius agglutinin A chain by site-directed mutagenesis. Pro(199) Of amphiphilic alpha-helix H impairs protein synthesis inhibitory activity

Abrus agglutinin (AAG), a low-toxicity protein from the plant Abrus precatorius, is less lethal than abrina (ABRa) in mice (LD(50) = 5 mg/kg versus 20 microg/kg of body weight). Nucleotide sequence analysis of a cDNA clone encoding full-length AAG showed an open reading frame with 1641 base pairs, corresponding to a 547-amino acid residue preproprotein containing a signal peptide and a linker region (two amino acid residues) between the AAG-A and AAG-B subunits. AAG had high homology to ABRa (77.8%). The 13 amino acid residues involved in catalytic function, which are highly conserved among abrins and ricins, were also conserved within AAG-A. The protein synthesis inhibitory activity of AAG-A (IC(50) = 3.5 nM) was weaker than that of ABRa-A (0.05 nM). Molecular modeling followed by site-directed mutagenesis showed that Pro(199) of AAG-A, located in amphiphilic helix H and corresponding to Asn(200) of ABRa-A, can induce bending of helix H. This bending would presumably affect the binding of AAG-A to its target sequence, GpApGpAp, in the tetraloop structure of the 28 S rRNA subunit and could be one of the major factors contributing to the relatively weak protein synthesis inhibitory activity and toxicity of AAG.

A wound-inducible gene from Salix viminalis coding for a trypsin inhibitor

A gene designated swin1.1 has been isolated by screening a Salix viminalis genomic library with a heterologous probe, win3 from Populus. The region sequenced included the entire coding sequence for a protein with 199 amino acids plus the promoter and terminator. At the 5' end of the coding region is a sequence that encodes a hydrophobic region of 25-30 amino acids, that could form a signal peptide. A putative TATAA box and polyadenylator sequence were identified. Introns were absent. The gene product showed similarities with serine protease inhibitors from the Kunitz family and especially with win3 from wounded leaves of Populus. Southern blot analysis indicated that swin1.1 is a member of a clustered gene family, swin1. An oligonucleotide corresponding to the putative hypervariable region towards the carboxyl end when used as a probe in Southern hybridization showed high specificity for swin1.1. Expression of the swin1.1 gene was enhanced in wounded leaves. The swin1.1 coding region without the signal sequence was highly expressed in Escherichia coli and the protein showed inhibitory activity against trypsin but at most slight activity against the other proteases tested. A systemically induced protein, SVTI, with inhibitor activity against trypsin, was isolated from Salix leaves by affinity chromatography on a column of trypsin-Sepharose 4B and N-terminal sequenced. It corresponded with the translated swin1.1 gene at 16 of the 19 amino acid sites, suggesting that SVTI is encoded by another member of the swin1 gene family.

Cloning and expression of the gene encoding Acacia confusa trypsin inhibitor that is active without post-translational proteolysis

A recombinant plasmid containing the coding regions for Acacia confusa trypsin inhibitor (ACTI) has been constructed and expressed in Escherichia coli cells, as a fusion protein between ACTI and glutathione S-transferase (GST). The GST-fusion was produced as a soluble protein which did not require denaturing agents such as urea to solubilize it. The recombinant ACTI (reACTI) was obtained by treating the GST-fusion protein with thrombin. Both the reACTI and fusion protein have a strong inhibitory effect on trypsin activity without post-translational proteolysis.