This work presents the selection and characterization of erythropoietin (EPO)-binding cyclic peptide ligands. The sequences were selected by screening a focused library of cyclic depsipeptides cyclo[(N-Ac)Dap(A)-X-X-AE], whose structure and amino acid compositions were tailored to mimic the EPO receptor. The sequences identified through library screening were synthesized on chromatographic resin and characterized via binding-and-elution studies against EPO to select a pool of candidate ligands. Sequences with higher hydrophobicity consistently showed stronger binding to EPO, with the exception of FSLLSH, which was noted for its lower hydrophobicity and high EPO binding. Mutagenesis studies performed on FSLLSH with natural and non-natural amino acid substitutions led to the identification of critical EPO-binding determinants, and the discovery of new peptide ligands. In particular, histidine-scanning mutagenesis performed on three lead sequences yielded the discovery of variants whose EPO-binding is more pH-sensitive, which facilitates EPO recovery. Selected ligands were studied to correlate the elution yield to the salinity of the binding buffer and the elution pH. Elution yields were consistently higher when EPO binding was performed at low ionic strength. The crystal structures of lead cyclic peptides were docked in silico against EPO to estimate the binding affinity in solution. Isotherm adsorption studies performed on FSLLSH indicated that the cyclic version of the ligand (K=0.46μM) has a higher affinity for EPO than its corresponding linear variant (K=1.44μM). Collectively, these studies set the stage for use of the cyclic peptide ligands as EPO purification and detection tools.
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http://dx.doi.org/10.1016/j.chroma.2017.04.019 | DOI Listing |
JACS Au
December 2024
Laboratory of Bioorganic Chemistry, National Institutes of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States.
Methods that enable the on-demand synthesis of biologically active molecules offer the potential for a high degree of control over the timing and context of target activation; however, such approaches often require extensive engineering to implement. Tools to restrict the localization of assembly also remain limited. Here we present a new approach for stimulus-induced ligand assembly that helps to address these challenges.
View Article and Find Full Text PDFFront Physiol
December 2024
National Heart and Lung Institute, Imperial College London, London, United Kingdom.
Introduction: Adrenergic activation of protein kinase A (PKA) in cardiac muscle targets the sarcolemma, sarcoplasmic reticulum, and contractile apparatus to increase contractile force and heart rate. In the thin filaments of the contractile apparatus, cardiac troponin I (cTnI) Ser22 and Ser23 in the cardiac-specific N-terminal peptide (NcTnI: residues 1 to 32) are the targets for PKA phosphorylation. Phosphorylation causes a 2-3 fold decrease of affinity of cTn for Ca associated with a higher rate of Ca dissociation from cTnC leading to a faster relaxation rate of the cardiac muscle (lusitropy).
View Article and Find Full Text PDFFront Immunol
December 2024
Department of Pediatrics, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China.
Objective: To investigate serum TL1A levels and their correlation with Th17 cells, IL-17, and IL-21 in children with Graves' disease (GD).
Methods: Thirty-seven children (12 males and 25 females) aged 9-14 years with newly diagnosed and untreated GD were enrolled in this study. Serum TL1A, IL-17, and IL-21 levels were measured using enzyme-linked immunosorbent assay (ELISA).
Sci Rep
December 2024
Department of Anatomy, Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand.
SARS-CoV-2, the cause of COVID-19, primarily targets lung tissue, leading to pneumonia and lung injury. The spike protein of this virus binds to the common receptor on susceptible tissues and cells called the angiotensin-converting enzyme-2 (ACE2) of the angiotensin (ANG) system. In this study, we produced chimeric Macrobrachium rosenbergii nodavirus virus-like particles, presenting a short peptide ligand (ACE2tp), based on angiotensin-II (ANG II), on their outer surfaces to allow them to specifically bind to ACE2-overexpressing cells called ACE2tp-MrNV-VLPs.
View Article and Find Full Text PDFColloids Surf B Biointerfaces
December 2024
Laboratory of Applied Toxicology, Center of Toxins, Immune-Response and Cell Signaling - CeT-ICS/CEPID, Butantan Institute São Paulo, São Paulo, SP CEP 05503-900, Brazil; Postgraduate Program Interunits in Biotechnology, USP/IPT/IBU, São Paulo, SP, Brazil. Electronic address:
Background: Irresponsible and wholesale use of antimicrobial agents is the principal cause of the emergence of strains of resistant microorganisms to traditional drugs. Oligoventin is a neutral peptide isolated from spider eggs of Phoneutria nigriventer, with antimicrobial activity against Gram-positive, Gram-negative, and yeast organisms. However, the molecular target and pathways of antimicrobial activity are still unknown.
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