Estudos estruturais experimentais e teóricos com proteínas do veneno da serpente Bothrops jararacussu
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2006-11-22
Autores
Magro, Angelo José [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho foram realizados estudos estruturais experimentais e teóricos com a BthA-I e a BjussuMP-I, duas proteínas isoladas do veneno de Bothrops jararacussu. A proteína BthA-I é uma fosfolipase A2 (PLA2) ácida com elevada atividade catalítica e que possui a capacidade de inibir a agregação de plaquetas e reduzir a pressão arterial. Cristais da BthA-I nativa e de sua forma quimicamente modificada pelo pBPB (brometo de p-bromofenacila), um conhecido inibidor de a PLA2s que também é capaz de suprimir os mecanismos farmacológicos próprios desta proteína, foram obtidos e submetidos a experimentos de difração de raios-X. A estrutura cristalina da BthA-I foi elucidada a 1,9 Å de resolução e o processamento dos dados experimentais revelou a presença de dois monômeros na unidade assimétrica. A análise estrutural destes monômeros revelou que a BthA-I dimérica possui uma conformação oligomérica distinta das demais PLA2s, onde os sítios catalíticos da molécula encontram-se expostos ao solvente. Apesar das condições de cristalização da BthA-I nativa, é possível sugerir que a forma dimérica desta proteína seja aquela encontrada predominantemente in vivo. A determinação estrutural da BthA-I quimicamente modificada pelo pBPB a 1,85 Å de resolução revelou a presença inequívoca de moléculas de inibidor covalentemente ligadas aos resíduos His48, localizados nos sítios de ligação de substrato dos dois monômeros do complexo. Três regiões do complexo BthA-I/pBPB são estruturalmente alteradas pela ligação do inibidor: os loops de ligação de Ca++ e as regiões de β-wing C-terminais. Estas mudanças estruturais são provavelmente derivadas da conformação oligomérica apresentada pelo complexo, cuja disposição pode explicar a supressão das atividades farmacológicas da BthA-I...
In this work were performed experimental and theoretical structural studies with BthA-I and BjussuMP-I, two proteins from the venom of Bothrops jararacussu. BthA-I, a high catalytic acidic phospholipase A2 (PLA2) with platelet aggregation inhibition, anticoagulant and hypotensive properties, was crystallized in its native form and complexed to pBPB (p-bromophenacyl bromide), a well-known inhibitor of PLA2s which also abolishes the biochemical activities of this protein. The crystal structure of BthA-I native was solved at 1.9 Å and the data processing showed two monomers in the unit cell. A novel dimeric conformation of this native protein with the active sites of the monomers exposed to the solvent was observed. Despite of the conditions used in the crystallization experiments, it is possible to suggest that the dimeric form must be predominantly found in vivo. The structural determination of BthA-I chemically modified by pBPB at 1.85 Å revealed the unambiguous identification of inhibitor molecules covalently bound to residues His48 in the substrate-binding clefts of both monomers of the complex. Three regions of BthA-I/pBPB complex are structurally altered by the binding of the inhibitor: the Ca++ -binding loops, the β-wings and the C-terminal regions. These structural changes are probably derived from the oligomeric state presented by the complex, which could explain the abolition of pharmacological activities of the pBPB-chemically modified BthA-I. A residue present in the “pancreatic” loops (Lys69), which is usually related to the anticoagulant effect of the BthA-I, is in the dimeric interface of the complex, supporting this hypothesis regarding the abolition of this and other activities caused by pBPB. The theoretical BjussuMP-I catalytic domain, a P-III metalloprotease, was built through folding recognition... (Complete abstract click electronic access below)
In this work were performed experimental and theoretical structural studies with BthA-I and BjussuMP-I, two proteins from the venom of Bothrops jararacussu. BthA-I, a high catalytic acidic phospholipase A2 (PLA2) with platelet aggregation inhibition, anticoagulant and hypotensive properties, was crystallized in its native form and complexed to pBPB (p-bromophenacyl bromide), a well-known inhibitor of PLA2s which also abolishes the biochemical activities of this protein. The crystal structure of BthA-I native was solved at 1.9 Å and the data processing showed two monomers in the unit cell. A novel dimeric conformation of this native protein with the active sites of the monomers exposed to the solvent was observed. Despite of the conditions used in the crystallization experiments, it is possible to suggest that the dimeric form must be predominantly found in vivo. The structural determination of BthA-I chemically modified by pBPB at 1.85 Å revealed the unambiguous identification of inhibitor molecules covalently bound to residues His48 in the substrate-binding clefts of both monomers of the complex. Three regions of BthA-I/pBPB complex are structurally altered by the binding of the inhibitor: the Ca++ -binding loops, the β-wings and the C-terminal regions. These structural changes are probably derived from the oligomeric state presented by the complex, which could explain the abolition of pharmacological activities of the pBPB-chemically modified BthA-I. A residue present in the “pancreatic” loops (Lys69), which is usually related to the anticoagulant effect of the BthA-I, is in the dimeric interface of the complex, supporting this hypothesis regarding the abolition of this and other activities caused by pBPB. The theoretical BjussuMP-I catalytic domain, a P-III metalloprotease, was built through folding recognition... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Serpente - Veneno, Fosfolipases A2, Biologia molecular estrutural, Metaloproteases
Como citar
MAGRO, Angelo José. Estudos estruturais experimentais e teóricos com proteínas do veneno da serpente Bothrops jararacussu. 2006. 85 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Biociências de Botucatu, 2006.