hbgp

Glossoscolex paulistus hemoglobin (HbGp) was studied by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). DLS melting curves were measured for met-HbGp at different concentrations. SAXS temperature studies were performed for oxy-, cyanomet- and met-HbGp forms, at several pH values. At pH 5.0 and 6.0, the scattering curves are identical from 20 to 60 °C, and Rg is 108 Å, independent of the oxidation form. At pH 7.0, protein denaturation and aggregation occurs above 55 °C and 60 °C, for oxy and met-HbGp, respectively...

The stability of the Glossoscolex paulistus hemoglobin (HbGp), in two iron oxidation states (and three forms), as monitored by optical absorption, fluorescence emission and circular dichroism (CD) spectroscopies, in the presence of the chaotropic agent urea, is studied. HbGp oligomeric dissociation, denaturation and iron oxidation are observed. CD data show that the cyanomet-HbGp is more stable than the oxy-form. Oxy- and cyanomet-HbGp show good fits on the basis of a two state model with critical urea concentrations at 220-222 nm of 5...

Giant extracellular hemoglobins present high redox stability due to their supramolecular architecture, high number of polypeptide chains and great compaction of protein subunits. The oligomeric assembly and the changes in the polypeptidic structure can influence the autoxidation rate of the heme proteins, being that different nucleophiles can act in this process due to pH alterations. In the present work, we have studied the autoxidation rate of whole Glossoscolex paulistus (HbGp) giant extracellular hemoglobin, as well as the autoxidation rate of the isolated d monomer of HbGp studied regarding pH variations...

Glossoscolex paulistus is a free-living earthworm encountered in south-east Brazil. Its oxygen transport requirements are undertaken by a giant extracellular haemoglobin, or erythrocruorin (HbGp), which has an approximate molecular mass of 3.6 MDa and, by analogy with its homologue from Lumbricus terrestris (HbLt), is believed to be composed of a total of 180 polypeptide chains. In the present work the full 3.6 MDa particle in its cyanomet state was purified and crystallized using sodium citrate or PEG8000 as precipitant...

The giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) has a molecular mass (M) of 3600±100 kDa and a standard sedimentation coefficient (s20,w0) of 58 S, estimated by analytical ultracentrifugation (AUC). In the present work, further AUC studies were developed for HbGp, at pH 10.0, which favors oligomeric dissociation into lower M species. The HbGp oligomer is formed by globin chains a, b, c and d plus the linker chains. The pure monomeric fraction, subunit d, and HbGp at pH 10.0, in the presence of β-mercaptoethanol, were also studied...

Glossoscolex paulistus hemoglobin (HbGp) was studied by dynamic light scattering (DLS), optical absorption spectroscopy (UV-VIS) and differential scanning calorimetry (DSC). At pH 7.0, cyanomet-HbGp is very stable, no oligomeric dissociation is observed, while denaturation occurs at 56°C, 4°C higher as compared to oxy-HbGp. The oligomeric dissociation of HbGp occurs simultaneously with some protein aggregation. Kinetic studies for oxy-HbGp using UV-VIS and DLS allowed to obtain activation energy (E(a)) values of 278-262 kJ/mol (DLS) and 333 kJ/mol (UV-VIS)...

Natural rubber production in Hevea brasiliensis is determined by both tapping and ethephon frequencies. It is affected by a complex physiological disorder called tapping panel dryness. This syndrome is likely to be induced by environmental and latex harvesting stresses. Defence responses, including rubber biosynthesis, are dramatically mediated by wounding, jasmonate and ethylene (ET), among other factors. Using real-time RT-PCR, the effects of wounding, methyl jasmonate (MeJA) and ET on the relative transcript abundance of a set of 25 genes involved in their signalling and metabolic pathways were studied in the bark of 3-month-old epicormic shoots...

The extracellular hemoglobin from Glossoscolex paulistus (HbGp) has a molecular mass of 3.6 MDa. It has a high oligomeric stability at pH 7.0 and low autoxidation rates, as compared to vertebrate hemoglobins. In this work, fluorescence and light scattering experiments were performed with the three oxidation forms of HbGp exposed to acidic pH. Our focus is on the HbGp stability at acidic pH and also on the determination of the isoelectric point (pI) of the protein. Our results show that the protein in the cyanomet form is more stable than in the other two forms, in the whole pH range...

The giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) is constituted by subunits containing heme groups with molecular masses (M) in the range of 15 to 19 kDa, monomers of 16 kDa (d), and trimers of 51 to 52 kDa (abc) linked by nonheme structures named linkers of 24 to 32 kDa (L). HbGp is homologous to Lumbricus terrestris hemoglobin (HbLt). Several reports propose M of HbLt in the range of 3.6 to 4.4 MDa. Based on subunits M determined by mass spectrometry and assuming HbGp stoichiometry of 12(abcd)(3)L(3) (Vinogradov model) plus 144 heme groups, a value of M for HbGp oligomer of 3560 kDa can be predicted...

The present article is focused on the transitions of ferric heme species of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) induced by successive alterations in pH, involving alkaline and acid mediums. Electron paramagnetic resonance (EPR) is the spectroscopy used to evaluate the transitions that occur in the first coordination sphere of ferric ion as a consequence of ligand changes in a wide range of pH, since this tool is very sensitive to slight changes that occur in the heme pocket of paramagnetic species...

The extracellular hemoglobin of Glossoscolex paulistus (HbGp) is constituted of subunits containing heme groups, monomers and trimers, and nonheme structures, called linkers, and the whole protein has a minimum molecular mass near 3.1 x 10(6) Da. This and other proteins of the same family are useful model systems for developing blood substitutes due to their extracellular nature, large size, and resistance to oxidation. HbGp samples were studied by dynamic light scattering (DLS). In the pH range 6.0-8.0, HbGp is stable and has a monodisperse size distribution with a z-average hydrodynamic diameter (D(h)) of 27 +/- 1 nm...

The present work is focused on the complex ferric heme species equilibrium of the giant extracellular hemoglobin from Glossoscolex paulistus (HbGp) in alkaline medium. EPR, UV-vis and CD spectroscopies were used in order to characterize the ferric heme species formed as a consequence of the medium alkalization as well as the oligomeric changes occurring simultaneously with heme transitions. EPR experiments allowed us to characterize the different hemichrome species in equilibrium, illustrating the small difference in spin state of this species and the complexity of the equilibira involving hemoglobin ferric species...

The giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) is constituted by approximately 144 subunits containing heme groups with molecular masses in the range of 16-19kDa forming a monomer (d) and a trimer (abc), and around 36 non-heme structures, named linkers (L). Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF-MS) analysis was performed recently, to obtain directly information on the molecular masses of the different subunits from HbGp in the oxy-form. This technique demonstrated structural similarity between HbGp and the widely studied hemoglobin of Lumbricus terrestris (HbLt)...

The present work focuses on the interaction between the zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp). Electronic optical absorption, fluorescence emission and circular dichroism spectroscopy techniques, together with Gel-filtration chromatography, were used in order to evaluate the oligomeric dissociation as well as the autoxidation of HbGp as a function of the interaction with HPS. A peculiar behavior was observed for the HPS-HbGp interaction: a complex ferric species formation equilibrium was promoted, as a consequence of the autoxidation and oligomeric dissociation processes...

In this work, MALDI-TOF-MS analysis was performed to obtain information on the molecular mass of the different subunits from the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy-form. Experiments were performed for the whole protein at pH 7.0, for the partially dissociated protein at pH 9.0, and for the fraction obtained from gel filtration in Sephadex G-200, at pH 9.0, corresponding to the isolated monomer d. Besides that, experiments were performed for the whole protein treated with 2-mercaptoethanol in order to monitor the effects of reduction of the disulfide bonds, which are expected to maintain the trimer (abc) in the native molecule...

The effects of two ionic surfactants on the oligomeric structure of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy - form have been studied through the use of several spectroscopic techniques such as electronic optical absorption, fluorescence emission, light scattering, and circular dichroism. The use of anionic sodium dodecyl sulphate (SDS) and cationic cethyltrimethyl ammonium chloride (CTAC) has allowed to differentiate the effects of opposite headgroup charges on the oligomeric structure dissociation and hemoglobin autoxidation...

The effect of the anionic surfactant sodium dodecyl sulfate (SDS) on the autoxidation process of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) is addressed in the present work. The complex oligomeric assembly of hemoglobin subunits may influence the autoxidation rate and the exponential decay behavior. Kinetic studies were developed using UV-vis measurements at 415 nm. These spectroscopic measurements are analyzed at two pH values, 7.0 and 9.0, where the hemoglobin presents different oligomeric assembly...