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A reagent for affinity labelling of the ATP-binding site in glutathione synthetase captures two flexible glycine-rich loops, revealing their structure.
Recent NMR structures of bovine immunodeficiency viral TAR RNA–Tat peptide complexes have revealed a new β-hairpin RNA recognition motif. These complexes exhibit intriguing new variations on the recurring themes in nucleic acid recognition.
The crystal structure of zeamatin, and comparisons within the family, suggest most PR-5 proteins have an electrostatically polarized surface which may be responsible for antifungal activity.
Rubisco's CO2 cofactor is involved in divalent -metal binding, activity regulation and probably also in the catalytic chemistry. Recent studies of the CO2- and metal-binding site in the absence of phosphorylated ligands provide a structural understanding of the unusual activation mechanism.
The difference in amino-acid sequence and inferred molecular mechanisms between the pair of EF-hands in BM-40 and those of other EF-hand proteins force us to reconsider the evolutionary and functional relationships among the members of this diverse family of proteins.
The EF-hand is a highly conserved Ca2+-binding motif found in many cytosolic Ca2+-modulated proteins. Here we report the crystal structure at 2.0 Å resolution of the carboxy-terminal domain of human BM-40 (SPARC, osteonectin), an extracellular matrix protein containing an EF-hand pair. The two EF-hands interact canonically but their detailed structures are unusual. In the first EF-hand a one-residue insertion is accommodated by a cis-peptide bond and by substituting a carboxylate by a peptide carbonyl as a Ca2+ ligand. The second EF-hand is stabilized by a disulphide bond. The EF-hand pair interacts tightly with an amphiphilic amino-terminal helix, reminiscent of target peptide binding by calmodulin. The present structure defines a novel protein module occurring in several other extracellular proteins.