Structural insights into somatostatin receptor 5 bound with cyclic peptides.

Somatostatin receptor 5 (SSTR5) is highly expressed in ACTH-secreting pituitary adenomas and is an important drug target for the treatment of Cushing's disease. Two cyclic SST analog peptides (pasireotide and octreotide) both can activate SSTR5 and SSTR2. Pasireotide is preferential binding to SSTR5 than octreotide, while octreotide is biased to SSTR2 than SSTR5.

Identification and characterization of a novel hydroxylamine oxidase, DnfA, that catalyzes the oxidation of hydroxylamine to N.

Nitrogen (N) gas in the atmosphere is partially replenished by microbial denitrification of ammonia. Recent study has shown that Alcaligenes ammonioxydans oxidizes ammonia to dinitrogen via a process featuring the intermediate hydroxylamine, termed "Dirammox" (direct ammonia oxidation). However, the unique biochemistry of this process remains unknown.

A mirror-image protein-based information barcoding and storage technology.

A mirror-image protein-based information barcoding and storage technology wherein D-amino acids are used to encode information into mirror-image proteins that are chemically synthesized is described. These mirror-image proteins were then fused into various materials from which information-encoded objects were produced. Subsequently, the mirror-image proteins were extracted from the objects using biotin-streptavidin resin-mediated specific enrichment and cleaved using an Ni(II)-mediated selective peptide cleavage.

The New Salicylaldehyde ,-Propanedithioacetal Ester Enables N-to-C Sequential Native Chemical Ligation and Ser/Thr Ligation for Chemical Protein Synthesis.

The combination of distinct peptide ligation techniques to facilitate chemical protein synthesis represents one of the long-standing goals in the field. A new combination ligation method of N-to-C sequential native chemical ligation and Ser/Thr ligation (NCL-STL) is described for the first time. This method relies on the peptide salicylaldehyde ,-propanedithioacetal (SAL)-ester prepared by a new 1,3-propanedithiol-mediated reaction.

Synthesis of Disulfide Surrogate Peptides Incorporating Large-Span Surrogate Bridges Through a Native-Chemical-Ligation-Assisted Diaminodiacid Strategy.

The use of synthetic bridges as surrogates for disulfide bonds has emerged as a practical strategy to obviate the poor stability of some disulfide-containing peptides. However, peptides incorporating large-span synthetic bridges are still beyond the reach of existing methods. Herein, we report a native chemical ligation (NCL)-assisted diaminodiacid (DADA) strategy that enables the robust generation of disulfide surrogate peptides incorporating surrogate bridges up to 50 amino acids in length.

Chemical Synthesis of Native S-Palmitoylated Membrane Proteins through Removable-Backbone-Modification-Assisted Ser/Thr Ligation.

The preparation of native S-palmitoylated (S-palm) membrane proteins is one of the unsolved challenges in chemical protein synthesis. Herein, we report the first chemical synthesis of S-palm membrane proteins by removable-backbone-modification-assisted Ser/Thr ligation (RBM -assisted STL). This method involves two critical steps: 1) synthesis of S-palm peptides by a new γ-aminobutyric acid based RBM (RBM ) strategy, and 2) ligation of the S-palm RBM-modified peptides to give the desired S-palm product by the STL method.

Chemical synthesis of membrane proteins by the removable backbone modification method.

Chemical synthesis can produce membrane proteins bearing specifically designed modifications (e.g., phosphorylation, isotope labeling) that are difficult to obtain through recombinant protein expression approaches.

Removable Backbone Modification Method for the Chemical Synthesis of Membrane Proteins.

Chemical synthesis can produce water-soluble globular proteins bearing specifically designed modifications. These synthetic molecules have been used to study the biological functions of proteins and to improve the pharmacological properties of protein drugs. However, the above advances notwithstanding, membrane proteins (MPs), which comprise 20-30% of all proteins in the proteomes of most eukaryotic cells, remain elusive with regard to chemical synthesis.

Chemical Synthesis of Diubiquitin-Based Photoaffinity Probes for Selectively Profiling Ubiquitin-Binding Proteins.

Biochemical studies of cellular processes involving polyubiquitin have gained increasing attention. More tools are needed to identify ubiquitin (Ub)-binding proteins. We report diazirine-based photoaffinity probes that can capture Ub-binding proteins in cell lysates, and show that diazirines are preferable to aryl azides as the photo-crosslinking group, since they decrease non-selective capture.

Efficient synthesis of longer Aβ peptides via removable backbone modification.

Longer amyloid-beta (Aβ) peptides (43 to 49 amino acids) play essential roles in the pathology of Alzheimer's disease (AD). The difficulty in the preparation of longer Aβ peptides is still an obstacle to elucidate their roles in AD. Herein we report a robust and efficient strategy for the chemical synthesis of longer Aβ peptides (Aβ48 and Aβ49).

Synthesis of l- and d-Ubiquitin by One-Pot Ligation and Metal-Free Desulfurization.

Native chemical ligation combined with desulfurization has become a powerful strategy for the chemical synthesis of proteins. Here we describe the use of a new thiol additive, methyl thioglycolate, to accomplish one-pot native chemical ligation and metal-free desulfurization for chemical protein synthesis. This one-pot strategy was used to prepare ubiquitin from two or three peptide segments.

Robust Chemical Synthesis of Membrane Proteins through a General Method of Removable Backbone Modification.

Chemical protein synthesis can provide access to proteins with post-translational modifications or site-specific labelings. Although this technology is finding increasing applications in the studies of water-soluble globular proteins, chemical synthesis of membrane proteins remains elusive. In this report, a general and robust removable backbone modification (RBM) method is developed for the chemical synthesis of membrane proteins.

Peptide toxins and small-molecule blockers of BK channels.

Large conductance, Ca(2+)-activated potassium (BK) channels play important roles in the regulation of neuronal excitability and the control of smooth muscle contractions. BK channels can be activated by changes in both the membrane potential and intracellular Ca(2+) concentrations. Here, we provide an overview of the structural and pharmacological properties of BK channel blockers.

Phospho-selective mechanisms of arrestin conformations and functions revealed by unnatural amino acid incorporation and (19)F-NMR.

Specific arrestin conformations are coupled to distinct downstream effectors, which underlie the functions of many G-protein-coupled receptors (GPCRs). Here, using unnatural amino acid incorporation and fluorine-19 nuclear magnetic resonance ((19)F-NMR) spectroscopy, we demonstrate that distinct receptor phospho-barcodes are translated to specific β-arrestin-1 conformations and direct selective signalling. With its phosphate-binding concave surface, β-arrestin-1 'reads' the message in the receptor phospho-C-tails and distinct phospho-interaction patterns are revealed by (19)F-NMR.

Total chemical synthesis of the site-selective azide-labeled [I66A]HIV-1 protease.

The first total chemical synthesis of the site-selective azide-labeled [I66A]HIV-1 protease is described by native chemical ligation. Chemical synthesis of azide-labeled proteins would provide useful protein tools for biochemical, biophysical or medical studies.

Diaminodiacid Bridges to Improve Folding and Tune the Bioactivity of Disulfide-Rich Peptides.

Disulfide-rich peptides containing three or more disulfide bonds are promising therapeutic and diagnostic agents, but their preparation is often limited by the tedious and low-yielding folding process. We found that a single cystine-to-diaminodiacid replacement could significantly increase the folding efficiency of disulfide-rich peptides and thus improve their production yields. The practicality of this strategy was demonstrated by the synthesis and folding of derivatives of the μ-conotoxin SIIIA, the preclinical hormone hepcidin, and the trypsin inhibitor EETI-II.

Expedient total synthesis of small to medium-sized membrane proteins via Fmoc chemistry.

Total chemical synthesis provides a unique approach for the access to uncontaminated, monodisperse, and more importantly, post-translationally modified membrane proteins. In the present study we report a practical procedure for expedient and cost-effective synthesis of small to medium-sized membrane proteins in multimilligram scale through the use of automated Fmoc chemistry. The key finding of our study is that after the attachment of a removable arginine-tagged backbone modification group, the membrane protein segments behave almost the same as ordinary water-soluble peptides in terms of Fmoc solid-phase synthesis, ligation, purification, and mass spectrometry characterization.