Structure of the Mg-chelatase cofactor GUN4 reveals a novel hand-shaped fold for porphyrin binding.
PLoS Biol
; 3(5): e151, 2005 May.
Article
en En
| MEDLINE
| ID: mdl-15884974
In plants, the accumulation of the chlorophyll precursor Mg-protoporphyrin IX (Mg-Proto) in the plastid regulates the expression of a number of nuclear genes with functions related to photosynthesis. Analysis of the plastid-to-nucleus signaling activity of Mg-Proto in Arabidopsis thaliana led to the discovery of GUN4, a novel porphyrin-binding protein that also dramatically enhances the activity of Mg-chelatase, the enzyme that synthesizes Mg-Proto. GUN4 may also play a role in both photoprotection and the cellular shuttling of tetrapyrroles. Here we report a 1.78-A resolution crystal structure of Synechocystis GUN4, in which the porphyrin-binding domain adopts a unique three dimensional fold with a "cupped hand" shape. Biophysical and biochemical analyses revealed the specific site of interaction between GUN4 and Mg-Proto and the energetic determinants for the GUN4.Mg-Proto interaction. Our data support a novel protective function for GUN4 in tetrapyrrole trafficking. The combined structural and energetic analyses presented herein form the physical-chemical basis for understanding GUN4 biological activity, including its role in the stimulation of Mg-chelatase activity, as well as in Mg-Proto retrograde signaling.
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1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Porfirinas
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Arabidopsis
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Proteínas de Arabidopsis
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Péptidos y Proteínas de Señalización Intracelular
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Liasas
Idioma:
En
Revista:
PLoS Biol
Asunto de la revista:
BIOLOGIA
Año:
2005
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos