title: Crystal structure of Arabidopsis PII reveals novel structural elements unique to plants.
abstract: The 1.9 A resolution crystal structure of PII from Arabidopsis thaliana reveals for the first time the molecular structure of a widely conserved regulator of carbon and nitrogen metabolism from a eukaryote. The structure provides a framework for understanding the arrangement of highly conserved residues shared with PII proteins from bacteria, archaea, and red algae as well as residues conserved only in plant PII. Most strikingly, a highly conserved segment at the N-terminus that is found only in plant PII forms numerous interactions with the alpha2 helix and projects from the surface of the homotrimer opposite to that occupied by the T-loop. In addition, solvent-exposed residues near the T-loop are highly conserved in plants but differ in prokaryotes. Several residues at the C-terminus that are also highly conserved only in plants contribute part of the ATP-binding site and likely participate in an ATP-induced conformational change. Structures of PII also reveal how citrate and malonate bind near the triphosphate binding site occupied by ATP in bacterial and archaeal PII proteins.
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Mizuno
authors.forename: Byron
authors.initials: B
authors.lastname: Berenger
authors.forename: Greg B G
authors.initials: GB
authors.lastname: Moorhead
authors.forename: Kenneth K-S
authors.initials: KK
authors.lastname: Ng
mesh_terms: D000595:Amino Acid Sequence; D019343:Citric Acid / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D008314:Malonates / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D008314:Malonates; D045332:Photosystem II Protein Complex; D019343:Citric Acid; C030290:malonic acid; D017851:Phosphotransferases (Carboxyl Group Acceptor); C018721:acetylglutamate kinase