RESUMO
Mannheimia haemolytica is the main etiological bacterial agent in ruminant respiratory disease. M. haemolytica secretes leukotoxin, lipopolysaccharides, and proteases, which may be targeted to treat infections. We recently reported the purification and in vivo detection of a 110 kDa Zn metalloprotease with collagenase activity (110-Mh metalloprotease) in a sheep with mannheimiosis, and this protease may be an important virulence factor. Due to the increase in the number of multidrug-resistant strains of M. haemolytica, new alternatives to antibiotics are being explored; one option is lactoferrin (Lf), which is a multifunctional iron-binding glycoprotein from the innate immune system of mammals. Bovine apo-lactoferrin (apo-bLf) possesses many properties, and its bactericidal and bacteriostatic effects have been highlighted. The present study was conducted to investigate whether apo-bLf inhibits the secretion and proteolytic activity of the 110-Mh metalloprotease. This enzyme was purified and sublethal doses of apo-bLf were added to cultures of M. haemolytica or co-incubated with the 110-Mh metalloprotease. The collagenase activity was evaluated using zymography and azocoll assays. Our results showed that apo-bLf inhibited the secretion and activity of the 110-Mh metalloprotease. Molecular docking and overlay assays showed that apo-bLf bound near the active site of the 110-Mh metalloprotease, which affected its enzymatic activity.
Assuntos
Lactoferrina , Mannheimia haemolytica , Metaloproteases , Proteólise , Lactoferrina/metabolismo , Lactoferrina/farmacologia , Metaloproteases/metabolismo , Metaloproteases/antagonistas & inibidores , Animais , Apoproteínas/metabolismo , Apoproteínas/química , Simulação de Acoplamento Molecular , Ovinos , Bovinos , Colagenases/metabolismo , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/química , Zinco/metabolismoRESUMO
Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder worldwide, and the therapeutic is focused on several approaches including the inhibition of fibril formation by small compounds, avoiding the formation of cytotoxic oligomers. Thus, we decided to explore the capacity of compounds carrying catechol moieties to inhibit the progression of α-synuclein. Overall, the compounds rosmarinic acid (1), carnosic acid (2), carnosol (3), epiisorosmanol (4), and rosmanol (5) avoid the progression of fibril formation assessed by Thiofavine T (ThT), and atomic force microscopy images showed that morphology is influenced for the actions of compounds over fibrillization. Moreover, ITC experiments showed a Kd varying from 28 to 51 µM, the ΔG showed that the reaction between compounds and α-syn is spontaneous, and ΔH is associated with an exothermic reaction, suggesting the interactions of hydrogen bonds among compounds and α-syn. Docking experiments reinforce this idea showing the intermolecular interactions are mostly hydrogen bonding within the sites 2, 9, and 3/13 of α-synuclein, and compounds 1 and 5. Thus, compound 1, rosmarinic acid, interestingly interacts better with site 9 through catechol and Lysines. In cultured Raw 264. 7 cells, the presence of compounds showed that most of them can promote cell differentiation, especially rosmarinic acid, and rosmanol, both preserving tubulin cytoskeleton. However, once we evaluated whether or not the aggregates pre-treated with compounds could prevent the disruption of microtubules of Raw 264.7 cells, only pre-treated aggregates with rosmarinic acid prevented the disruption of the cytoskeleton. Altogether, we showed that especially rosmarinic acid not only inhibits α-syn but stabilizes the remaining aggregates turning them into not-toxic to Raw 264.7 cells suggesting a main role in cell survival and antigen processing in response to external α-syn aggregates.
Assuntos
Cinamatos , Depsídeos , Microtúbulos , Ácido Rosmarínico , alfa-Sinucleína , Depsídeos/farmacologia , Depsídeos/química , Depsídeos/isolamento & purificação , Cinamatos/química , Cinamatos/farmacologia , Cinamatos/síntese química , Animais , Camundongos , Células RAW 264.7 , Microtúbulos/efeitos dos fármacos , Microtúbulos/metabolismo , Estrutura Molecular , alfa-Sinucleína/metabolismo , alfa-Sinucleína/antagonistas & inibidores , Relação Estrutura-Atividade , Relação Dose-Resposta a Droga , Sobrevivência Celular/efeitos dos fármacos , Simulação de Acoplamento MolecularRESUMO
Light chain amyloidosis is a conformational disease caused by the abnormal proliferation and deposition of antibody light chains as amyloid fibers in organs and tissues. The effect of Cu(II) binding to the model recombinant protein 6aJL2-R24G was previously characterized in our group, and we found an acceleration of the aggregation kinetics of the protein. In this study, in order to confirm the Cu(II) binding sites, histidine variants of 6aJL2-R24G were prepared and the effects of their interaction with Cu(II) were analyzed by circular dichroism, fluorescence spectroscopy, isothermal calorimetry titrations, and molecular dynamics simulations. Confirming our earlier work, we found that His8 and His99 are the highest affinity Cu(II) binding sites, and that Cu(II) binding to both sites is a cooperative event.
Assuntos
Cobre , Histidina , Ligação Proteica , Cobre/metabolismo , Cobre/química , Histidina/química , Histidina/metabolismo , Humanos , Sítios de Ligação , Simulação de Dinâmica Molecular , Cadeias Leves de Imunoglobulina/metabolismo , Cadeias Leves de Imunoglobulina/genética , Cadeias Leves de Imunoglobulina/química , Amiloidose de Cadeia Leve de Imunoglobulina/metabolismo , Amiloidose de Cadeia Leve de Imunoglobulina/genética , Amiloidose/metabolismo , Amiloidose/genética , CinéticaRESUMO
Cataract formation is a slow accumulative process due to protein aggregates promoted by different factors over time. Zinc and copper ions have been reported to induce the formation of aggregates opaque to light in the human gamma D crystallin (HγD) in a concentration and temperature dependent manner. In order to gain insight into the mechanism of metal-induced aggregation of HγD under conditions that mimic more closely the slow, accumulative process of the disease, we have studied the non-equilibrium process with the minimal metal dose that triggers HγD aggregation. Using a wide variety of biophysics techniques such as turbidimetry, dynamic light scattering, fluorescence, nuclear magnetic resonance and computational methods, we obtained information on the molecular mechanisms for the formation of aggregates. Zn(II) ions bind to different regions at the protein, probably with similar affinities. This binding induces a small conformational rearrangement within and between domains and aggregates via the formation of metal bridges without any detectable unfolded intermediates. In contrast, Cu(II)-induced aggregation includes a lag time, in which the N-terminal domain partially unfolds while the C-terminal domain and parts of the N-terminal domain remain in a native-like conformation. This partially unfolded intermediate is prone to form the high-molecular weight aggregates. Our results clearly show that different external factors can promote protein aggregation following different pathways.
RESUMO
Light-chain amyloidosis (AL) is one of the most common systemic amyloidoses, and it is characterized by the deposition of immunoglobulin light chain (LC) variable domains as insoluble amyloid fibers in vital organs and tissues. The recombinant protein 6aJL2-R24G contains λ6a and JL2 germline genes and also contains the Arg24 by Gly substitution. This mutation is present in 25% of all amyloid-associated λ6 LC cases, reduces protein stability, and increases the propensity to form amyloid fibers. In this study, it was found that the interaction of 6aJL2-R24G with Cu(II) decreases the thermal stability of the protein and accelerates the amyloid fibril formation, as observed by fluorescence spectroscopy. Isothermal calorimetry titration showed that Cu(II) binds to the protein with micromolar affinity. His99 may be one of the main Cu(II) interaction sites, as observed by nuclear magnetic resonance spectroscopy. The binding of Cu(II) to His99 induces larger fluctuations of the CDR1 and loop Câ³, as shown by molecular dynamics simulations. Thus, Cu(II) binding may be inducing the loss of interactions between CDR3 and CDR1, making the protein less stable and more prone to form amyloid fibers. This study provides insights into the mechanism of metal-induced aggregation of the 6aJL2-R24G protein and sheds light on the bio-inorganic understanding of AL disease.
RESUMO
Late embryogenesis abundant (LEA) proteins accumulate in plants during adverse conditions and their main attributed function is to confer tolerance to stress. One of the deleterious effects of the adverse environment is the accumulation of metal ions to levels that generate reactive oxygen species, compromising the survival of cells. AtLEA4-5, a member of group 4 of LEAs in Arabidopsis, is an intrinsically disordered protein. It has been shown that their N-terminal region is able to undergo transitions to partially folded states and prevent the inactivation of enzymes. We have characterized metal ion binding to AtLEA4-5 by circular dichroism, electronic absorbance spectroscopy (UV-vis), electron paramagnetic resonance, dynamic light scattering, and isothermal titration calorimetry. The data shows that AtLEA4-5 contains a single binding site for Ni(II), while Zn(II) and Cu(II) have multiple binding sites and promote oligomerization. The Cu(II) interacts preferentially with histidine residues mostly located in the C-terminal region with moderate affinity and different coordination modes. These results and the lack of a stable secondary structure formation indicate that an ensemble of conformations remains accessible to the metal for binding, suggesting the formation of a fuzzy complex. Our results support the multifunctionality of LEA proteins and suggest that the C-terminal region of AtLEA4-5 could be responsible for antioxidant activity, scavenging metal ions under stress conditions while the N-terminal could function as a chaperone.
RESUMO
The prion protein coordinates copper with high affinity in the regions encompassing residues 92-99 (GGGTHSQW) and 106-115 (KTNMKHMAGA). Cu(II) binding to these sites involves the coordination of the His96/His111 imidazole ring and backbone deprotonated amides that precede the His residue. Such a coordination arrangement involves the formation of hexa- and penta-membered cycles that provide further stabilization of the metal-peptide complex. The purpose of the present study is to introduce a methylene group in the peptide backbone, to evaluate the impact of increasing the size of these cycles in Cu(II) binding. Thus, a ß-alanine residue was inserted at different positions preceding the His residue in these prion fragments, and their Cu(II) coordination properties were assessed by UV-Visible absorption, circular dichroism, and electron paramagnetic resonance. Spectroscopic data show that the insertion of a methylene group leads to a completely different Cu(II) coordination that involves the His96/His111 imidazole ring and nitrogen or oxygen atoms provided by the peptide backbone towards the C-terminal. This study clearly shows that two main factors determine the nature of Cu(II)-peptide complexes involving an anchoring His residue and deprotonated amides from the backbone chain: i) the stabilization of Cu(II)-peptide complexes due to the formation of cyclic structures (i.e. chelate effect) and ii) the nature of the residues associated to the deprotonated amide groups that participate in metal ion coordination.
Assuntos
Complexos de Coordenação/química , Cobre/química , Peptídeos/química , Príons/química , beta-Alanina/química , Cátions Bivalentes , Dicroísmo Circular , Espectroscopia de Ressonância de Spin Eletrônica , Histidina/química , Humanos , Peptídeos/síntese química , Ligação Proteica , Domínios e Motivos de Interação entre ProteínasRESUMO
Metal ions play a wide range of important functional roles in biology, and they often serve as cofactors in enzymes. Some of the metal ions that are essential for life are strongly associated with proteins, forming obligate metalloproteins, while others may bind to proteins with relatively low affinity. The spectroscopic tools presented in this chapter are suitable to study metal ion-protein interactions. Metal sites in proteins are usually low symmetry centers that differentially absorb left and right circularly polarized light. The combination of electronic absorption and circular dichroism (CD) in the UV-visible region allows the characterization of electronic transitions associated with the metal-protein complex, yielding information on the geometry and nature of the metal-ligand interactions. For paramagnetic metal centers in proteins, electron paramagnetic resonance (EPR) is a powerful tool that provides information on the chemical environment around the unpaired electron(s), as it relates to the electronic structure and geometry of the metal-protein complex. EPR can also probe interactions between the electron spin and nuclear spins in the vicinity, yielding valuable information on some metal-ligand interactions. This chapter describes each spectroscopic technique and it provides the necessary information to design and implement the study of metal ion-protein interactions by electronic absorption, CD, and EPR.
Assuntos
Complexos de Coordenação/química , Elétrons , Metais Pesados/química , Proteínas/química , Sítios de Ligação , Dicroísmo Circular , Espectroscopia de Ressonância de Spin Eletrônica , Cinética , Ligação Proteica , Espectrofotometria , Temperatura , TermodinâmicaRESUMO
The prion protein (PrP(C)) is implicated in the spongiform encephalopathies in mammals, and it is known to bind Cu(II) at the N-terminal region. The region around His111 has been proposed to be key for the conversion of normal PrP(C) to its infectious isoform PrP(Sc). The principal aim of this study is to understand the role of protons and methionine residues 109 and 112 in the coordination of Cu(II) to the peptide fragment 106-115 of human PrP, using different spectroscopic techniques (UV-vis absorption, circular dichroism, and electron paramagnetic resonance) in combination with detailed electronic structure calculations. Our study has identified a proton equilibrium with a pK(a) of 7.5 associated with the Cu(II)-PrP(106-115) complex, which is ascribed to the deprotonation of the Met109 amide group, and it converts the site from a 3NO to a 4N equatorial coordination mode. These findings have important implications as they imply that the coordination environment of this Cu binding site at physiological pH is a mixture of two species. This study also establishes that Met109 and Met112 do not participate as equatorial ligands for Cu, and that Met112 is not an essential ligand, while Met109 plays a more important role as a weak axial ligand, particularly for the 3NO coordination mode. A role for Met109 as a highly conserved residue that is important to regulate the protonation state and redox activity of this Cu binding site, which in turn would be important for the aggregation and amyloidogenic properties of the protein, is proposed.