α(V)ß(3) integrin crystal structures and their functional implications.
Biochemistry
; 51(44): 8814-28, 2012 Nov 06.
Article
em En
| MEDLINE
| ID: mdl-23106217
ABSTRACT
Many questions about the significance of structural features of integrin α(V)ß(3) with respect to its mechanism of activation remain. We have determined and re-refined crystal structures of the α(V)ß(3) ectodomain linked to C-terminal coiled coils (α(V)ß(3)-AB) and four transmembrane (TM) residues in each subunit (α(V)ß(3)-1TM), respectively. The α(V) and ß(3) subunits with four and eight extracellular domains, respectively, are bent at knees between the integrin headpiece and lower legs, and the headpiece has the closed, low-affinity conformation. The structures differ in the occupancy of three metal-binding sites in the ßI domain. Occupancy appears to be related to the pH of crystallization, rather than to the physiologic regulation of ligand binding at the central, metal ion-dependent adhesion site. No electron density was observed for TM residues and much of the α(V) linker. α(V)ß(3)-AB and α(V)ß(3)-1TM demonstrate flexibility in the linker between their extracellular and TM domains, rather than the previously proposed rigid linkage. A previously postulated interface between the α(V) and ß(3) subunits at their knees was also not supported, because it lacks high-quality density, required rebuilding in α(V)ß(3)-1TM, and differed markedly between α(V)ß(3)-1TM and α(V)ß(3)-AB. Together with the variation in domain-domain orientation within their bent ectodomains between α(V)ß(3)-AB and α(V)ß(3)-1TM, these findings are compatible with the requirement for large structural changes, such as extension at the knees and headpiece opening, in conveying activation signals between the extracellular ligand-binding site and the cytoplasm.
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Estrutura Terciária de Proteína
/
Integrina alfaVbeta3
Tipo de estudo:
Prognostic_studies
Limite:
Animals
/
Humans
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
2012
Tipo de documento:
Article
País de afiliação:
Estados Unidos