Rab/Ypt guanosine triphosphatases (GTPases) represent a family of key membrane traffic regulators in eukaryotic cells whose function is governed by the guanosine diphosphate (GDP) dissociation inhibitor (RabGDI). Using a combination of chemical synthesis and protein engineering, we generated and crystallized the monoprenylated Ypt1:RabGDI complex. The structure of the complex was solved to 1.5 angstrom resolution and provides a structural basis for the ability of RabGDI to inhibit the release of nucleotide by Rab proteins. Isoprenoid binding requires a conformational change that opens a cavity in the hydrophobic core of its domain II. Analysis of the structure provides a molecular basis for understanding a RabGDI mutant that causes mental retardation in humans.

In eukaryotic cells Rab/Ypt GTPases represent a family of key membrane traffic controllers that associate with their targeted membranes via C-terminally conjugated geranylgeranyl groups. GDP dissociation inhibitor (GDI) is a general and essential regulator of Rab recycling that extracts prenylated Rab proteins from membranes at the end of their cycle of activity and facilitates their delivery to the donor membranes. Here, we present the structure of a complex between GDI and a doubly prenylated Rab protein. We show that one geranylgeranyl residue is deeply buried in a hydrophobic pocket formed by domain II of GDI, whereas the other lipid is more exposed to solvent and is skewed across several atoms of the first moiety. Based on structural information and biophysical measurements, we propose mechanistic and thermodynamic models for GDI and Rab escort protein-mediated interaction of RabGTPase with intracellular membranes.

The total synthesis of (+)-lithospermic acid is described. The efficient synthesis features an asymmetric alkylation via C-H bond activation to assemble the dihydrobenzofuran core of the natural product. This was accomplished via a chiral imine-directed C-H bond functionalization and represents the first application of this C-H activation method to natural product synthesis. Furthermore, a challenging deprotection of a late-stage permethylated lithospermic acid was achieved.

The site-and chemoselective immobilization of proteins through regions of the macromolecules that are not involved in interactions with other molecules is preferable or even required for the application of protein arrays in proteomics research. [1][2][3][4] Recently, expressed protein ligation was employed for this purpose, [5] and Raines and co-workers [6] and Bertozzi and co-workers [7] demonstrated the use of the Staudinger ligation [8, 9] for protein immobilization by means of a two-step process in which a peptide is first immobilized followed by noncovalent binding of a protein to the peptide sequence.Herein, we report the successful site-selective covalent immobilization of proteins by reaction of the azide-modified C terminus of a protein generated by expressed protein

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The site-and chemoselective immobilization of proteins through regions of the macromolecules that are not involved in interactions with other molecules is preferable or even required for the application of protein arrays in proteomics research. [1][2][3][4] Recently, expressed protein ligation was employed for this purpose, [5] and Raines and co-workers [6] and Bertozzi and co-workers [7] demonstrated the use of the Staudinger ligation [8, 9] for protein immobilization by means of a two-step process in which a peptide is first immobilized followed by noncovalent binding of a protein to the peptide sequence.Herein, we report the successful site-selective covalent immobilization of proteins by reaction of the azide-modified C terminus of a protein generated by expressed protein

Salvianolic acid B and lithospermic acid B are the major components of Salvia miltiorrhiza, which is one of the most popular herbal traditional medicines in Asian countries. Salvianolic acid B and lithospermic acid B are reported to have identical structures except for the configurational assignments of two stereocenters. Through chemical correlation between a degradation product of salvianolic acid B and synthetic material, the absolute configuration of salvianolic acid B has been corrected to establish that salvianolic acid B and lithospermic acid B are in fact the same compound.

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