Host defence peptides (HDPs) are evolutionarily conserved components of innate immunity. Human HDPs, produced by a variety of immune cells of hematopoietic and epithelial origin, are generally grouped into two families: beta structured defensins and variably-structured cathelicidins. We report the characterization of a very promising cryptic human HDP, here called GVF27, identified in 11-hydroxysteroid dehydrogenase-1 β-like protein.Conformational analysis of GVF27 and its propensity to bind endotoxins were performed by NMR, Circular Dichroism, Fluorescence and Dynamic Light Scattering experiments. Crystal violet and WST-1 assays, ATP leakage measurement and colony counting procedures were used to investigate antimicrobial, anti-biofilm, cytotoxicity and hemolytic activities. Anti-inflammatory properties were evaluated by ELISA.GVF27 possesses significant antibacterial properties on planktonic cells and sessile bacteria forming biofilm, as well as promising dose dependent abilities to inhibit attachment or eradicate existing mature biofilm. It is unstructured in aqueous buffer, whereas it tends to assume a helical conformation in mimic membrane environments as well as it is able to bind lipopolysaccharide (LPS) and lipoteichoic acid (LTA). Notably it is not toxic towards human and murine cell lines and triggers a significant innate immune response by attenuating expression levels of pro-inflammatory interleukins and release of nitric oxide in LPS induced macrophages.Human GVF27 may offer significant advantages as leads for the design of human-specific therapeutics.Human cryptic host defence peptides are naturally no immunogenic and for this they are a real alternative for solving the lack of effective antibiotics to control bacterial infections.

Two novel human antitumor immunoconjugates, engineered by fusion of a single-chain antibody fragment against human ErbB2 receptor, termed Erbicin, with either a human RNase or the Fc region of a human IgG(1), are selectively cytotoxic for ErbB2-positive cancer cells in vitro and in vivo. These Erbicin-derived immunoagents (EDIAs) do not show the most negative properties of Herceptin, the only humanized mAb against ErbB2 used in the therapy of breast carcinoma: cardiotoxicity and the inability to act on resistant tumors. These differences are probably attributable to the different ErbB2 epitopes recognized by EDIAs and Herceptin, respectively, as we have previously reported that they induce different signaling mechanisms that control tumor and cardiac cell viability. Thus, to accurately identify the novel epitope recognized by EDIAs, three independent and complementary methodologies were used. They gave coherent results, which are reported here: EDIAs bind to a different ErbB2 epitope than Herceptin and the other human/humanized antibodies against ErbB2 reported so far. The epitope has been successfully located in region 122-195 of extracellular domain I. These findings could lead to the identification of novel epitopes on ErbB2 that could be used as potential therapeutic targets to mitigate anti-ErbB2-associated cardiotoxicity and eventually overcome resistance.

Erbicin is a human anti-ErbB2 single-chain antibody fragment with high affinity and selectivity for ErbB2-positive cancer cells. Two anti-ErbB2 immunoconjugates, called Erb-hRNase and Erb-hcAb, have been prepared and found to be selectively cytotoxic on ErbB2-positive cancer cells in vitro and vivo. In Erb-hRNase, Erbicin is linked to a human RNase and in Erb-hcAb it is linked to the key structural and functional regions of a human IgG. Herceptin is an anti-ErbB2 humanised antibody successfully used in the immunotherapy of breast cancer. We report here that the Erbicin-derived immunoagents target on breast cancer cells an ErbB2 epitope different than that of Herceptin. This finding led us to verify the effects of Herceptin on breast cancer cells when it was used in combination with the Erbicin-derived immunoagents. The results indicated that in combination experiments the antitumour action of Herceptin and that of the novel agents were significantly increased in an additive fashion. An inspection of the mechanism of action of Erb-hRNase or Erb-hcAb combined with Herceptin provided evidence that the antibody combinations engendered an increased downregulation of the ErbB2 receptor, and led to an enhanced apoptotic cell death.

ABSTRACT Toluene o -xylene monooxygenase (ToMO) and phenol hydroxylase (PH) of Pseudomonas stutzeri OX1 act sequentially in a recombinant upper pathway for the degradation of aromatic hydrocarbons. The catalytic efficiency and regioselectivity of these enzymes optimize the degradation of growth substrates like toluene and o -xylene. For example, the sequential monooxygenation of o -xylene by ToMO and PH leads to almost exclusive production of 3,4-dimethylcatechol (3,4-DMC), the only isomer that can be further metabolized by the P. stutzeri meta pathway. We investigated the possibility of producing ToMO mutants with modified regioselectivity compared with the regioselectivity of the wild-type protein in order to alter the ability of the recombinant upper pathway to produce methylcatechol isomers from toluene and to produce 3,4-DMC from o -xylene. The combination of mutant (E103G)-ToMO and PH increased the production of 4-methylcatechol from toluene and increased the formation of 3,4-DMC from o -xylene. These data strongly support the idea that the products and efficiency of the metabolic pathway can be controlled not only through mutations that increase the catalytic efficiency of the enzymes involved but also through tuning the substrate specificity and regioselectivity of the enzymes. These findings are crucial for the development of future metabolic engineering strategies.

ABSTRACT The pathways for degradation of aromatic hydrocarbons are constantly modified by a variety of genetic mechanisms. Genetic studies carried out with Pseudomonas stutzeri OX1 suggested that the tou operon coding for toluene o -xylene monooxygenase (ToMO) was recently recruited into a preexisting pathway that already possessed the ph operon coding for phenol hydroxylase (PH). This apparently resulted in a redundancy of enzymatic activities, because both enzymes are able to hydroxylate (methyl)benzenes to (methyl)catechols via the intermediate production of (methyl)phenols. We investigated the kinetics and regioselectivity of toluene and o -xylene oxidation using Escherichia coli cells expressing ToMO and PH complexes. Our data indicate that in the recombinant system the enzymes act sequentially and that their catalytic efficiency and regioselectivity optimize the degradation of toluene and o -xylene, both of which are growth substrates. The main product of toluene oxidation by ToMO is p -cresol, the best substrate for PH, which catalyzes its transformation to 4-methylcatechol. The sequential action of the two enzymes on o -xylene leads, via the intermediate 3,4-dimethylphenol, to the exclusive production of 3,4-dimethylcatechol, the only dimethylcatechol isomer that can serve as a carbon and energy source after further metabolic processing. Moreover, our data strongly support a metabolic explanation for the acquisition of the ToMO operon by P. stutzeri OX1. It is possible that using the two enzymes in a concerted fashion confers on the strain a selective advantage based on the ability of the microorganism to optimize the efficiency of the use of nonhydroxylated aromatic hydrocarbons, such as benzene, toluene, and o -xylene.

ABSTRACT Degradation of aromatic hydrocarbons by aerobic bacteria is generally divided into an upper pathway, which produces dihydroxylated aromatic intermediates by the action of monooxygenases, and a lower pathway, which processes these intermediates down to molecules that enter the citric acid cycle. Bacterial multicomponent monooxygenases (BMMs) are a family of enzymes divided into six distinct groups. Most bacterial genomes code for only one BMM, but a few cases (3 out of 31) of genomes coding for more than a single monooxygenase have been found. One such case is the genome of Pseudomonas stutzeri OX1, in which two different monooxygenases have been found, phenol hydroxylase (PH) and toluene/ o -xylene monooxygenase (ToMO). We have already demonstrated that ToMO is an oligomeric protein whose subunits transfer electrons from NADH to oxygen, which is eventually incorporated into the aromatic substrate. However, no molecular data are available on the structure and on the mechanism of action of PH. To understand the metabolic significance of the association of two similar enzymatic activities in the same microorganism, we expressed and characterized this novel phenol hydroxylase. Our data indicate that the PH P component of PH transfers electrons from NADH to a subcomplex endowed with hydroxylase activity. Moreover, a regulatory function can be suggested for subunit PH M. Data on the specificity and the kinetic constants of ToMO and PH strongly support the hypothesis that coupling between the two enzymatic systems optimizes the use of nonhydroxylated aromatic molecules by the draining effect of PH on the product(s) of oxidation catalyzed by ToMO, thus avoiding phenol accumulation.

This paper describes the cloning of the genes coding for each component of the complex of toluene/o-xylene monooxygenase from Pseudomonas stutzeri OX1, their expression, purification and characterization. Moreover, the reconstitution of the active complex from the recombinant subunits has been obtained, and the functional role of each component in the electron transfer from the electron donor to molecular oxygen has been determined. The coexpression of subunits B, E and A leads to the formation of a subcomplex, named H, with a quaternary structure (BEA)2, endowed with hydroxylase activity. Tomo F component is an NADH oxidoreductase. The purified enzyme contains about 1 mol of FAD, 2 mol of iron, and 2 mol of acid labile sulfide per mol of protein, as expected for the presence of one [2Fe-2S] cluster, and exhibits a typical flavodoxin absorption spectrum. Interestingly, the sequence of the protein does not correspond to that previously predicted on the basis of DNA sequence. We have shown that this depends on minor errors in the gene sequence that we have corrected. C component is a Rieske-type ferredoxin, whose iron and acid labile sulfide content is in agreement with the presence of one [2Fe-2S] cluster. The cluster is very sensitive to oxygen damage. Mixtures of the subcomplex H and of the subunits F, C and D are able to oxidize p-cresol into 4-methylcathecol, thus demonstrating the full functionality of the recombinant subunits as purified. Finally, experimental evidence is reported which strongly support a model for the electron transfer. Subunit F is the first member of an electron transport chain which transfers electrons from NADH to C, which tunnels them to H subcomplex, and eventually to molecular oxygen.

Several members of the RNase A superfamily are endowed with antitumor activity, showing selective cytotoxicity toward several tumor cell lines. One of these is onconase, the smallest member of the RNase A superfamily, which is at present undergoing phase III clinical trials. We report here the expression of recombinant onconase in Escherichia coli inclusion bodies, the correct processing of the protein, followed by its purification in high yields. The recombinant protein has biological and catalytic properties identical to those of the natural enzyme.

Monomeric bovine pancreatic RNase A has been transformed into a dimeric ribonuclease with antitumor activity (Di Donato, A., Cafaro, V. and D'Alessio, G. (1994) J. Biol. Chem. 269, 17394–17396). This was accomplished by replacing the residues located in the RNase chain at positions 19, 28, 31, and 32, with proline, leucine, and two cysteine residues, respectively, i.e. those present at identical positions in the subunit of bovine seminal RNase, a dimeric RNase of the pancreatic‐type superfamily, endowed with a powerful antitumor action. However, as an antitumor agent this mutant dimeric RNase A is not as powerful as seminal RNase. We report here site‐directed mutagenesis experiments which have led to the identification of two other amino acid residues, glycine 38 and 111, whose substitution in the polypeptide chain of the first generation dimeric mutant of RNase A, is capable of conferring to the mutein the full cytotoxic activity characteristic of native seminal RNase.

Bovine seminal ribonuclease, BS-RNase, is a dimeric enzyme possessing very special biological actions. Its identical subunits possess more than 80 % of sequence identity with pancreatic RNase A. We prepared a monomeric and carboxyamidomethylated form of bovine seminal ribonuclease, MCAM-BS-RNase, in order to compare its thermodynamic stability with that of RNase A. DSC and CD measurements indicated that MCAM-BS-RNase has a reduced thermal stability with respect to RNase A.

Phytolacca dioica L. leaves produce at least two type-I ribosome-inactivating proteins. Each polypeptide chain is subjected to different post-translational modifications giving rise to PD-L1 and PD-L2, and PD-L3 and PD-L4, each polypeptide pair having the same primary structure. With the aim of exploiting the cytotoxic properties of these proteins as potential biological phytodrugs, a gene encoding PD-L4 was designed based on criteria expected to maximize the translation efficiency in tomato. The gene was constructed from 18 oligonucleotides and preliminarily expressed in Escherichia coli, using the T7 promoter system. The protein produced was insoluble and accumulated in inclusion bodies to about 300 mg/l of culture. Ribosome-inactivating activity was generated by controlled oxidation of the reduced and denatured protein. The recombinant protein was indistinguishable from natural PD-L4 as isolated from leaves of Phytolacca dioica, in both catalytic activity and primary structure.

Natural bovine seminal RNase possesses a potent antitumor action. We have mutagenized monomeric bovine pancreatic RNase A, devoid of any cytotoxic action, to insert residues present at corresponding positions in the subunit of dimeric, antitumor, seminal RNase. Like naturally dimeric seminal RNase, the mutant dimeric RNase display selective toxicity for malignant cells, which is absent in the monomeric mutants.

Four residues Pro19, Leu28, Cys31 and Cys32 proved to be the minimal structural requirements in determining the dimeric structure and the N-terminal segment swapping of bovine seminal ribonuclease, BS-RNase. We analyzed the content of secondary and tertiary structures in RNase A, P-RNase A, PL-RNase A, MCAM-PLCC-RNase A and MCAM-BS-RNase, performing near and far-UV CD spectra. It results that the five proteins have very similar native conformations. Thermal denaturation at pH 5.0 of the proteins, studied by means of CD measurements, proved reversible and well represented by the two-state N⇔D transition model. Thermodynamic data are discussed in the light of the structural information available for RNase A and BS-RNase.

A proline, a leucine, and two cysteine residues, introduced at positions 19, 28, 31, and 32 of bovine pancreatic RNase A, i.e. the positions occupied by these residues in the subunit of bovine seminal RNase, the only dimeric RNase of the pancreatic-type superfamily, transform monomeric RNase A into a dimeric RNase, endowed with the same ability of BS-RNase of swapping its N-terminal segments. The thermodynamic consequences of the progressive introduction of these four residues into RNase A polypeptide chain have been studied by comparing the temperature- and urea-induced denaturation of three mutants of RNase A with that of a stable monomeric derivative of BS-RNase. The denaturation processes proved reversible for all proteins, and well represented by the two-state N<-->D transition model. The progressive introduction of the four residues into RNase A led to a gradual shift of the protein stability toward that characteristic of monomeric BS-RNase, which, in turn, is markedly less stable than RNase A with respect to both temperature- and urea-induced denaturation. On the other hand, the thermal stability of a dimeric active mutant of RNase A is found to approach that of wild-type seminal RNase.

It has been previously shown that the antitumor action of bovine seminal ribonuclease (BS-RNase) is dependent on its dimeric structure. However, two distinct quaternary structures, each in equilibrium with the other, have been described for the enzyme: one in which the two subunits exchange their N-terminal ends, the other with no exchange. Antitumor activity assays, carried out on homogeneous quaternary forms of the enzyme, as well as on dimeric mutants of bovine pancreatic RNase A, reveal that another structural determinant of the antitumor activity of BS-RNase is the exchange of N-terminal ends between subunits.

Bovine seminal RNase (BS-RNase) is a dimeric member of the pancreatic-like ribonuclease superfamily, with antitumor activity. We report here that recombinant Met(-1) BS-RNase is a less potent cytotoxic factor, while structurally and catalytically indistinguishable from BS-RNase isolated from natural sources. Mature recombinant BS-RNase instead displays full antitumor action. This suggests that the conformation of the N-terminal region of BS-RNase is among the structural determinants of its antitumor action, in addition to its catalytic activity and its quaternary structure.

Residues P19, L28, C31, and C32 have been implicated (Di Donato A, Cafaro V, D'Alessio G, 1994, J Biol Chem 269:17394-17396; Mazzarella L, Vitagliano L, Zagari A, 1995, Proc Natl Acad Sci USA: forthcoming) with key roles in determining the dimeric structure and the N-terminal domain swapping of seminal RNase. In an attempt to have a clearer understanding of the structural and functional significance of these residues in seminal RNase, a series of mutants of pancreatic RNase A was constructed in which one or more of the four residues were introduced into RNase A. The RNase mutants were examined for: (1) the ability to form dimers; (2) the capacity to exchange their N-terminal domains; (3) resistance to selective cleavage by subtilisin; and (4) antitumor activity. The experiments demonstrated that: (1) the presence of intersubunit disulfides is both necessary and sufficient for engendering a stably dimeric RNase; (2) all four residues play a role in determining the exchange of N-terminal domains; (3) the exchange is the molecular basis for the RNase antitumor action; and (4) this exchange is not a prerequisite in an evolutionary mechanism for the generation of dimeric RNases.

A cDNA coding for bovine pancreatic RNase A was mutagenized to insert a proline, a leucine, and 2 cysteine residues, i.e. the residues present at corresponding positions in the subunit of seminal RNase, the only dimeric RNase of the pancreatic-type superfamily. The mutant, expressed in Escherichia coli, eventually aggregated into catalytically active dimers. Like naturally dimeric seminal RNase, at equilibrium the mutant dimeric RNase A adopted two quaternary structures (one with an exchange of the N-terminal segments between partner subunits, the other with no exchange) and displayed a selective toxicity for malignant cells, absent in the monomeric, parent protein.