Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, by infecting cells via the interaction of its spike protein (S) with the primary cell receptor angiotensin-converting enzyme (ACE2). To search for inhibitors of this key step in viral infection, we screened an in-house library of multivalent tryptophan derivatives. Using VSV-S pseudoparticles, we identified compound as a potent entry inhibitor lacking cellular toxicity.
View Article and Find Full Text PDFThe S:A222V point mutation, within the G clade, was characteristic of the 20E (EU1) SARS-CoV-2 variant identified in Spain in early summer 2020. This mutation has since reappeared in the Delta subvariant AY.4.
View Article and Find Full Text PDFP, a homotrimeric very ancient and highly widespread (bacteria, archaea, plants) key sensor-transducer protein, conveys signals of abundance or poorness of carbon, energy and usable nitrogen, converting these signals into changes in the activities of channels, enzymes, or of gene expression. P sensing is mediated by the P allosteric effectors ATP, ADP (and, in some organisms, AMP), 2-oxoglutarate (2OG; it reflects carbon abundance and nitrogen scarcity) and, in many plants, L-glutamine. Cyanobacteria have been crucial for clarification of the structural bases of P function and regulation.
View Article and Find Full Text PDFVitamin B -dependent genetic epilepsy was recently associated to mutations in PLPBP (previously PROSC), the human version of the widespread COG0325 gene that encodes TIM-barrel-like pyridoxal phosphate (PLP)-containing proteins of unclear function. We produced recombinantly, purified and characterized human PROSC (called now PLPHP) and its six missense mutants reported in epileptic patients. Normal PLPHP is largely a monomer with PLP bound through a Schiff-base linkage.
View Article and Find Full Text PDFThe Synechococcus elongatus COG0325 gene pipY functionally interacts with the nitrogen regulatory gene pipX. As a first step toward a molecular understanding of such interactions, we characterized PipY. This 221-residue protein is monomeric and hosts pyridoxal phosphate (PLP), binding it with limited affinity and losing it upon incubation with D-cycloserine.
View Article and Find Full Text PDFPCC 7942 is a paradigmatic model organism for nitrogen regulation in cyanobacteria. Expression of genes involved in nitrogen assimilation is positively regulated by the 2-oxoglutarate receptor and global transcriptional regulator NtcA. Maximal activation requires the subsequent binding of the co-activator PipX.
View Article and Find Full Text PDFPipX, an 89-residue protein, acts as a coactivator of the global nitrogen regulator NtcA in cyanobacteria. NtcA-PipX interactions are regulated by 2-oxoglutarate (2-OG), an inverse indicator of the ammonia abundance, and by P, a protein that binds to PipX at low 2-OG concentrations. The structure of PipX, when bound to NtcA or P, consists of an N-terminal, five-stranded β-sheet (conforming a Tudor-like domain), and two long α-helices.
View Article and Find Full Text PDFCyanobacteria, phototrophic organisms that perform oxygenic photosynthesis, perceive nitrogen status by sensing 2-oxoglutarate levels. PII, a widespread signaling protein, senses and transduces nitrogen and energy status to target proteins, regulating metabolism and gene expression. In cyanobacteria, under conditions of low 2-oxoglutarate, PII forms complexes with the enzyme N-acetyl glutamate kinase, increasing arginine biosynthesis, and with PII-interacting protein X (PipX), making PipX unavailable for binding and co-activation of the nitrogen regulator NtcA.
View Article and Find Full Text PDFSurface plasmon resonance monitoring of the binding of transcription factors cAMP receptor protein (CRP) and nitrogen control factor of cyanobacteria (NtcA) from Synechocystis sp. PCC6803 to promoter fragments of glnA, glnN (NtcA regulon) and cccS (CRP regulon), revealed exclusive CRP binding to cccS, whereas NtcA was bound to all three promoters with different affinities, which were strongly increased by the NtcA activator 2-oxoglutarate. Effective NtcA affinity for 2-oxoglutarate varied with the promoter.
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