Chloroplast acetyl-CoA carboxylase activity is 2-oxoglutarate-regulated by interaction of PII with the biotin carboxyl carrier subunit.
The PII protein is a signal integrator involved in the regulation of nitrogen metabolism in bacteria and plants. Upon sensing of cellular carbon and energy availability, PII conveys the signal by interacting with target proteins, thereby modulating their biological activity. Plant PII is located to plastids; therefore, to identify new PII target proteins, PII-affinity chromatography of soluble extracts from Arabidopsis leaf chloroplasts was performed. Several proteins were retained only when Mg-ATP was present in the binding medium and they were specifically released from the resin by application of a 2-oxoglutarate-containing elution buffer. Mass spectroscopy of SDS/PAGE-resolved protein bands identified the biotin carboxyl carrier protein subunits of the plastidial acetyl-CoA carboxylase (ACCase) and three other proteins containing a similar biotin/lipoyl-binding motif as putative PII targets. ACCase is a key enzyme initiating the synthesis of fatty acids in plastids. In in vitro reconstituted assays supplemented with exogenous ATP, recombinant Arabidopsis PII inhibited chloroplastic ACCase activity, and this was completely reversed in the presence of 2-oxoglutarate, pyruvate, or oxaloacetate. The inhibitory effect was PII-dose-dependent and appeared to be PII-specific because ACCase activity was not altered in the presence of other tested proteins. PII decreased the V(max) of the ACCase reaction without altering the K(m) for acetyl-CoA. These data show that PII function has evolved between bacterial and plant systems to control the carbon metabolism pathway of fatty acid synthesis in plastids.
Feria Bourrellier
Ana Belen
AB
Institut de Biotechnologie des Plantes, Centre National de Recherche Scientifique Unité Mixte de Recherche 8618, Université Paris-Sud 11, 91405 Orsay Cedex, France.
Valot
Benoit
B
Guillot
Alain
A
Ambard-Bretteville
Françoise
F
Vidal
Jean
J
Hodges
Michael
M
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000103:Acetyl-CoA Carboxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001710:Biotin / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology*; D007656:Ketoglutaric Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000648:ultrastructure; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D007656:Ketoglutaric Acids; D051922:PII Nitrogen Regulatory Proteins; C473074:PII protein, Arabidopsis; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D001710:Biotin; D000105:Acetyl Coenzyme A; D000103:Acetyl-CoA Carboxylase