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PMID: 15884974 Published · ppublish English Journal Article Research Support, N.I.H., Extramural Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S.

Structure of the Mg-chelatase cofactor GUN4 reveals a novel hand-shaped fold for porphyrin binding.

PLoS biology ·Vol. 3 ·No. 5 ·2005-05-00 ·Pages e151

Verdecia MA, Larkin RM, Ferrer JL, Riek R, Chory J, Noel JP

Abstract

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.

MeSH Terms
Arabidopsis/enzymology,metabolism Arabidopsis Proteins/genetics,metabolism Binding Sites Chlorophyll/metabolism Cloning, Molecular Intracellular Signaling Peptides and Proteins/genetics,metabolism Lyases/metabolism Porphyrins/metabolism Protein Folding Recombinant Proteins/metabolism Restriction Mapping
Chemicals
Arabidopsis Proteins GUN4 protein, Arabidopsis Intracellular Signaling Peptides and Proteins Porphyrins Recombinant Proteins Chlorophyll Lyases magnesium chelatase
Authors & Affiliations
6 authors, click to expand affiliations / ORCID
Verdecia Mark A
Chemical Biology and Proteomics Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA.
Larkin Robert M
Ferrer Jean-Luc
Riek Roland
Chory Joanne
Noel Joseph P
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Article Info
Journal
PLoS biology
Abbr.
PLoS Biol
ISSN
1545-7885
DOI
10.1371/journal.pbio.0030151
Published
2005-05-00
Epub
2005-00-26
Pages
e151
Language
English
Region
United States
NLM ID
101183755
PMCID
PMC1084334
Subset
IM
Grants
Howard Hughes Medical Institute · United States
NCI NIH HHS · P01 CA054418 · United States
NCI NIH HHS · CA54418 · United States
Databases
PDB
1Y6I
External Links
PubMed source DOI: 10.1371/journal.pbio.0030151 PMC Full Text View journal details
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