Stereochemical analysis of the reaction catalyzed by human protein geranylgeranyl transferase

Selective oxidation of alcohol-d 1 to aldehyde-d 1 using MnO2

The selective oxidation of alcohol-d₁ to prepare aldehyde-d₁ was newly developed by means of NaBD₄ reduction/activated MnO₂ oxidation. Various aldehyde-d₁ derivatives including aromatic and unsaturated aldehyde-d₁ can be prepared with a high deuterium incorporation ratio (up to 98% D). Halogens (chloride, bromide, and iodide), alkene, alkyne, ester, nitro, and cyano groups in the substrates are tolerated under the mild conditions.

A facile method for deutrium incorporation into aldehydes by mild reduction of NaBD₄ of aldehydes and MnO₂ oxidation (98% D) is disclosed.

Membrane Lipid Composition: Effect on Membrane and Organelle Structure, Function and Compartmentalization and Therapeutic Avenues

Biological membranes are key elements for the maintenance of cell architecture and physiology. Beyond a pure barrier separating the inner space of the cell from the outer, the plasma membrane is a scaffold and player in cell-to-cell communication and the initiation of intracellular signals among other functions. Critical to this function is the plasma membrane compartmentalization in lipid microdomains that control the localization and productive interactions of proteins involved in cell signal propagation. In addition, cells are divided into compartments limited by other membranes whose integrity and homeostasis are finely controlled, and which determine the identity and function of the different organelles. Here, we review current knowledge on membrane lipid composition in the plasma membrane and endomembrane compartments, emphasizing its role in sustaining organelle structure and function. The correct composition and structure of cell membranes define key pathophysiological aspects of cells. Therefore, we explore the therapeutic potential of manipulating membrane lipid composition with approaches like membrane lipid therapy, aiming to normalize cell functions through the modification of membrane lipid bilayers.

Protein Lipidation: Occurrence, Mechanisms, Biological Functions, and Enabling Technologies

Protein lipidation, including cysteine prenylation, N-terminal glycine myristoylation, cysteine palmitoylation, and serine and lysine fatty acylation, occurs in many proteins in eukaryotic cells and regulates numerous biological pathways, such as membrane trafficking, protein secretion, signal transduction, and apoptosis. We provide a comprehensive review of protein lipidation, including descriptions of proteins known to be modified and the functions of the modifications, the enzymes that control them, and the tools and technologies developed to study them. We also highlight key questions about protein lipidation that remain to be answered, the challenges associated with answering such questions, and possible solutions to overcome these challenges.

Protein prenylation: enzymes, therapeutics, and biotechnology applications

Protein prenylation is a ubiquitous covalent post-translational modification found in all eukaryotic cells, comprising attachment of either a farnesyl or a geranylgeranyl isoprenoid. It is essential for the proper cellular activity of numerous proteins, including Ras family GTPases and heterotrimeric G-proteins. Inhibition of prenylation has been extensively investigated to suppress the activity of oncogenic Ras proteins to achieve antitumor activity. Here, we review the biochemistry of the prenyltransferase enzymes and numerous isoprenoid analogs synthesized to investigate various aspects of prenylation and prenyltransferases. We also give an account of the current status of prenyltransferase inhibitors as potential therapeutics against several diseases including cancers, progeria, aging, parasitic diseases, and bacterial and viral infections. Finally, we discuss recent progress in utilizing protein prenylation for site-specific protein labeling for various biotechnology applications.

Chemoselective immobilization of proteins by microcontact printing and bio-orthogonal click reactions

Herein, a combination of microcontact printing of functionalized alkanethiols and site-specific modification of proteins is utilized to chemoselectively immobilize proteins onto gold surfaces, either by oxime- or copper-catalyzed alkyne-azide click chemistry. Two molecules capable of click reactions were synthesized, an aminooxy-functionalized alkanethiol and an azide-functionalized alkanethiol, and self-assembled monolayer (SAM) formation on gold was confirmed by IR spectroscopy. The alkanethiols were then individually patterned onto gold surfaces by microcontact printing. Site-specifically modified proteins-horse heart myoglobin (HHMb) containing an N-terminal α-oxoamide and a red fluorescent protein (mCherry-CVIA) with a C-terminal alkyne-were immobilized by incubation onto respective stamped functionalized alkanethiol patterns. Pattern formation was confirmed by fluorescence microscopy.

Prenyltransferase Inhibitors: Treating Human Ailments from Cancer to Parasitic Infections

The posttranslational modification of protein prenylation is a covalent lipid modification on the C-terminus of substrate proteins that serves to enhance membrane affinity. Oncogenic proteins such as Ras have this modification and significant effort has been placed into developing inhibitors of the prenyltransferase enzymes for clinical therapy. In addition to cancer therapy, prenyltransferase inhibitors have begun to find important therapeutic uses in other diseases, including progeria, hepatitis C and D, parasitic infections, and other maladies. This review will trace the evolution of prenyltransferase inhibitors from their initial use as cancer therapeutics to their expanded applications for other diseases.

A minimalist substrate for enzymatic peptide and protein conjugation

Recently a number of nonnatural prenyl groups containing alkynes and azides have been developed as handles to perform click chemistry on proteins and peptides ending in the sequence "CAAX", where C is a cysteine that becomes alkylated, A is an aliphatic amino acid and X is any amino acid. When such molecules are modified, a tag containing a prenyl analogue and the "CAAX box" sequence remains. Here we report the synthesis of an alkyne-containing substrate comprised of only nine nonhydrogen atoms. This substrate was synthesized in six steps from 3-methylbut-2-en-1-ol and has been enzymatically incorporated into both proteins and peptides by using protein farnesyltransferase. After prenylation the final three amino acids required for enzymatic recognition can be removed by using carboxypeptidase Y, leaving a single residue (the cysteine from the "CAAX box") and the prenyl analogue as the only modifications. We also demonstrate that this small tag minimizes the impact of the modification on the solubility of the targeted protein. Hence, this new approach should be useful for applications in which the presence of a large tag hinders the modified protein's solubility, reactivity, or utility.

Thematic review series: lipid posttranslational modifications. Structural biology of protein farnesyltransferase and geranylgeranyltransferase type I

More than 100 proteins necessary for eukaryotic cell growth, differentiation, and morphology require posttranslational modification by the covalent attachment of an isoprenoid lipid (prenylation). Prenylated proteins include members of the Ras, Rab, and Rho families, lamins, CENPE and CENPF, and the gamma subunit of many small heterotrimeric G proteins. This modification is catalyzed by the protein prenyltransferases: protein farnesyltransferase (FTase), protein geranylgeranyltransferase type I (GGTase-I), and GGTase-II (or RabGGTase). In this review, we examine the structural biology of FTase and GGTase-I (the CaaX prenyltransferases) to establish a framework for understanding the molecular basis of substrate specificity and mechanism. These enzymes have been identified in a number of species, including mammals, fungi, plants, and protists. Prenyltransferase structures include complexes that represent the major steps along the reaction path, as well as a number of complexes with clinically relevant inhibitors. Such complexes may assist in the design of inhibitors that could lead to treatments for cancer, viral infection, and a number of deadly parasitic diseases.

Structure of mammalian protein geranylgeranyltransferase type-I

Protein geranylgeranyltransferase type-I (GGTase-I), one of two CaaX prenyltransferases, is an essential enzyme in eukaryotes. GGTase-I catalyzes C-terminal lipidation of >100 proteins, including many GTP- binding regulatory proteins. We present the first structural information for mammalian GGTase-I, including a series of substrate and product complexes that delineate the path of the chemical reaction. These structures reveal that all protein prenyltransferases share a common reaction mechanism and identify specific residues that play a dominant role in determining prenyl group specificity. This hypothesis was confirmed by converting farnesyltransferase (15-C prenyl substrate) into GGTase-I (20-C prenyl substrate) with a single point mutation. GGTase-I discriminates against farnesyl diphosphate (FPP) at the product turnover step through the inability of a 15-C FPP to displace the 20-C prenyl-peptide product. Understanding these key features of specificity is expected to contribute to optimization of anti-cancer and anti-parasite drugs.

Coupling of isoprenoid triflates with organoboron nucleophiles: synthesis and biological evaluation of geranylgeranyl diphosphate analogues

The Suzuki coupling reaction has been used to introduce a methyl group derived from commercially available methylboronic acid into a vinyl triflate. This has led to a concise synthesis of all-trans-geranylgeraniol, with the key step being the palladium-catalyzed, silver-mediated methylation of triflate to give ethyl geranylgeranoate. This coupling protocol has also been used to produce the novel geranylgeranyl diphosphate (GGPP) analogue 3-phenyl-3-desmethylgeranylgeranyl diphosphate (3-PhGGPP, ). Our previously developed organocuprate coupling protocol has been used to introduce the cyclopropyl and tert-butyl moieties into the 3-position of vinyl triflate. The four GGPP analogues 3-vinyl-3-desmethylgeranylgeranyl diphosphate (3-vGGPP, ), 3-cyclopropyl-3-desmethylgeranylgeranyl diphosphate (3-cpGGPP, ), 3-tert-butyl-3-desmethyl-geranylgeranyl diphosphate (3-tbGGPP, ), and were then evaluated as potential inhibitors of recombinant yeast protein-geranylgeranyl transferase I (PGGTase I). The potential mechanism-based inhibitors 3-vGGPP and 3-cpGGPP did not exhibit time-dependent inactivation of PGGTase I. Instead, both analogues were alternative substrates, in accord with the interaction of the corresponding farnesyl analogues 3-vFPP and 3-cpFPP with PFTase. The tert-butyl and phenyl analogues were not substrates, but were instead competitive inhibitors of PGGTase I. Note that all four of the GGPP analogues were bound less tightly by the enzyme than the natural substrate, in contrast to the behavior of the 3-substituted FPP analogues.