Urea-induced unfolding of Glossoscolex paulistus hemoglobin, in oxy- and cyanomet-forms: A dissociation model

Autor(es)

Carvalho, Francisco A. O. ^[1] ; Carvalho, Jose Wilson P. ^[1] ; Santiago, Patricia S. ^{[1, 2]} ; Tabak, Marcel ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, Sao Paulo, SP - Brazil

^[2] Univ Estadual Paulista Julio de Mesquite Filho, Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: International Journal of Biological Macromolecules; v. 52, p. 340-348, JAN 2013.
• Citações Web of Science: 6

Resumo

The urea effect on the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) stability was studied by analytical ultracentrifugation (AUC) and small angle X-ray scattering (SAXS). AUC data show that the sedimentation coefficient distributions curves c (S), at 1.0 mol/L of urea, display a single peak at 57 S, associated to the undissociated protein. The increase in urea concentration, up to 4.0 mol/L, induces the appearance of smaller species, due to oligomeric dissociation. The sedimentation coefficients and molecular masses are 9.2 S and 204 kDa for the dodecamer (abcd)(3), 5.5 S and 69 kDa for the tetramer (abcd), 4.1 S and 52 kDa for the trimer (abc) and 2.0 S and 17 kDa for the monomer d, respectively. SAXS data show initially a decrease in the 1(0) values due to the oligomeric dissociation, and then, above 4.0 mol/L of denaturant, for oxy-HbGp, and above 6.0 mol/L for cyanomet-HbGp, an increase in the maximum dimension and gyration radius is observed, due to the unfolding process. According to AUC and SAXS data the HbGp unfolding is described by two phases: the first one, at low urea concentration, below 4.0 mol/L, characterizes the oligomeric dissociation, while the second one, at higher urea concentration, is associated to the unfolding of dissociated species. Our results are complementary to a recent report based on spectroscopic observations. (C) 2012 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 09/17261-6 - Estudo da estabilidade oligomérica da hemoglobina extracellular gigante de Glossoscolex paulistus (HbGp) na presença de agentes caotrópicos, surfactantes e caracterização das subunidades.
• Beneficiário: Francisco Adriano de Oliveira Carvalho
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 10/09719-0 - Estudos dos efeitos de surfactantes, do estado de oxidação do ferro e do pH do meio na estabilidade térmica da hemoglobina extracelular gigante de Glossoscolex paulistus (HbGp) na forma íntegra e de suas subunidades monômero d e trímero ABC
• Beneficiário: José Wilson Pires Carvalho
• Modalidade de apoio: Bolsas no Brasil - Doutorado