Comparative analysis of structural and dynamic properties of the loaded and unloaded hemophore HasA: functional implications.
J Mol Biol
; 376(2): 517-25, 2008 Feb 15.
Article
en En
| MEDLINE
| ID: mdl-18164722
A heme-acquisition system present in several Gram-negative bacteria requires the secretion of hemophores. These extracellular carrier proteins capture heme and deliver it to specific outer membrane receptors. The Serratia marcescens HasA hemophore is a monodomain protein that binds heme with a very high affinity. Its alpha/beta structure, as that of its binding pocket, has no common features with other iron- or heme-binding proteins. Heme is held by two loops L1 and L2 and coordinated to iron by an unusual ligand pair, H32/Y75. Two independent regions of the hemophore beta-sheet are involved in HasA-HasR receptor interaction. Here, we report the 3-D NMR structure of apoHasA and the backbone dynamics of both loaded and unloaded hemophore. While the overall structure of HasA is very similar in the apo and holo forms, the hemophore presents a transition from an open to a closed form upon ligand binding, through a large movement, of up to 30 A, of loop L1 bearing H32. Comparison of loaded and unloaded HasA dynamics on different time scales reveals striking flexibility changes in the binding pocket. We propose a mechanism by which these structural and dynamic features provide the dual function of heme binding and release to the HasR receptor.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Serratia marcescens
/
Proteínas Bacterianas
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Proteínas Portadoras
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Proteínas de la Membrana
Idioma:
En
Revista:
J Mol Biol
Año:
2008
Tipo del documento:
Article
País de afiliación:
Francia
Pais de publicación:
Países Bajos