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Cucumber Necrosis Virus (CNV) is a member of the genus Tombusvirus and has a monopartite positive-sense RNA genome packaged in a T=3 icosahedral particle. CNV is transmitted in nature via zoospores of the fungus Olpidium bornovanus. CNV undergoes a conformational change upon binding to the zoospore that is required for transmission, and specific polysaccharides on the zoospore surface have been implicated in binding. To better understand this transmission process, we have determined the atomic structure of CNV. As expected, being a member of the Tombusvirus genus, the core structure of CNV is highly similar to that of Tomato bushy stunt virus (TBSV), with major differences lying on the exposed loops. Also, as was seen with TBSV, CNV appears to have a calcium binding site between the subunits around the quasi-3-fold axes. However, unlike TBSV, there appears to be a novel zinc binding site within the β annulus formed by the N termini of the three C subunits at the icosahedral 3-fold axes. Two of the mutations causing defective transmission map immediately around this zinc binding site. The other mutations causing defective transmission and particle formation are mapped onto the CNV structure, and it is likely that a number of the mutations affect zoospore transmission by affecting conformational transitions rather than directly affecting receptor binding.
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http://dx.doi.org/10.1128/JVI.01965-13 | DOI Listing |
Physiology (Bethesda)
September 2025
Departments of Ophthalmology and Medicine, Stanford Cardiovascular Institute, Stanford University, Palo Alto, CA 94304.
Canonical activation of G-protein coupled receptors (GPCRs) by hormone binding occurs at the plasma membrane, resulting in the diffusion of second messengers to intracellular effector sites throughout the cell. In contrast, recent evidence suggests that functional GPCRs can induce signaling from distinct intracellular domains, contributing to specificity in signaling. Functional adrenergic receptors have been identified at intracellular sites in the cardiac myocyte such as endosomes, the sarcoplasmic reticulum, the Golgi and the inner nuclear membrane.
View Article and Find Full Text PDFSci Adv
September 2025
Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA.
Integrins bind ligands between their alpha (α) and beta (β) subunits and transmit signals through conformational changes. Early in chordate evolution, some α subunits acquired an "inserted" (I) domain that expanded integrin's ligand-binding repertoire but obstructed the ancestral ligand pocket, seemingly blocking conventional integrin activation. Here, we compare cryo-electron microscopy structures of apo and ligand-bound states of the I domain-containing αEβ integrin and the I domain-lacking αβ integrin to illuminate how the I domain intrinsically mimics an extrinsic ligand to preserve integrin function.
View Article and Find Full Text PDFBioinformatics
September 2025
Biocomputation and Complex Systems Physics Institute (BIFI)-Joint Unit GBsC-CSIC, University of Zaragoza, Zaragoza, 50018, Spain.
Motivation: The stability of protein interfaces influences protein dynamics and unfolding cooperativity. Although in some cases the dynamics of proteins can be deduced from their topology, much of the stability of an interface is related to the complementarity of the interacting parts. It is also important to note that proteins that display non-cooperative unfolding cannot be rationally stabilized unless the regions that unfold first are known.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
September 2025
Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
In eukaryotic systems, three major types of cell junctions have been well characterized. While bacterial adhesion mechanisms also exhibit remarkable diversity, the molecular processes that regulate the dynamic modulation of binding strength between elongated bacterial cells and host cells remain poorly understood. () utilizes the surface adhesin CbpF to interact with the highly expressed host receptors CEACAM1 and CEACAM5 on cancer cells to facilitate tumor colonization.
View Article and Find Full Text PDFDev Growth Differ
September 2025
Department of Biological Sciences, College of Arts, Sciences, and Education, Florida International University, Miami, Florida, USA.
Superoxide dismutases (SODs) are key regulators of reactive oxygen species (ROS) and redox balance. Although intracellular SODs have been extensively studied, growing attention has been directed toward understanding the roles of extracellular SODs in both Dictyostelium and mammalian systems. In Dictyostelium discoideum, SodC is a glycosylphosphatidylinositol (GPI)-anchored enzyme that modulates extracellular superoxide to regulate Ras, PI3K signaling, and cytoskeletal remodeling during directional cell migration.
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