Bacteriophages express endolysins which are the enzymes that hydrolyze peptidoglycan resulting in cell lysis and release of bacteriophages. Endolysins have acquired stringent substrate specificities, which have been attributed to cell wall binding domains (CBD). Although it has been realized that CBDs of bacteriophages that infect Gram-positive bacteria target cell wall carbohydrate structures, molecular mechanisms that confer selectivity are not understood.
View Article and Find Full Text PDFThe recombinant lysins of lytic phages, when applied externally to Gram-positive bacteria, can be efficient bactericidal agents, typically retaining high specificity. Their development as novel antibacterial agents offers many potential advantages over conventional antibiotics. Protein engineering could exploit this potential further by generating novel lysins fit for distinct target populations and environments.
View Article and Find Full Text PDFPlants use a highly evolved immune system to exhibit defense response against microbial infections. The plant TIR domain, together with the nucleotide-binding (NB) domain and/or a LRR region, forms a type of molecule, named resistance (R) proteins, that interact with microbial effector proteins and elicit hypersensitive responses against infection. Here, we report the first crystal structure of a plant TIR domain from Arabidopsis thaliana (AtTIR) solved at a resolution of 2.
View Article and Find Full Text PDFMacrophages detect pathogen infection via the activation of their plasma membrane-bound Toll-like receptor proteins (TLRs). The heterotypic interaction between the Toll/interleukin-1 receptor (TIR) domains of TLRs and adaptor proteins, like Myeloid differentiation primary response gene 88 (MyD88), is the first intracellular step in the signaling pathway of the mammalian innate immune response. The hetero-oligomerization of the TIRs of the receptor and adaptor brings about the activation of the transcription factor NF-kappaB, which regulates the synthesis of pro-inflammatory cytokines.
View Article and Find Full Text PDFBiochem Biophys Res Commun
May 2007
Based on protein sequence homology searches, we found a conserved open reading frame within the genome of several human pathogenic bacteria showing a resemblance to the mammalian TIR domain. We cloned, expressed, and characterized the corresponding gene product from Paracoccus denitrificans using several biophysical techniques. The protein consists of two independently folded domains.
View Article and Find Full Text PDFWe report a structural and functional analysis of the lambda prophage Ba02 endolysin (PlyL) encoded by the Bacillus anthracis genome. We show that PlyL comprises two autonomously folded domains, an N-terminal catalytic domain and a C-terminal cell wall-binding domain. We determined the crystal structure of the catalytic domain; its three-dimensional fold is related to that of the cell wall amidase, T7 lysozyme, and contains a conserved zinc coordination site and other components of the catalytic machinery.
View Article and Find Full Text PDFThe Escherichia coli chaperone Hsp33 contains a C-terminal zinc-binding domain that modulates activity by a so-called "redox switch". The oxidized form in the absence of zinc is active, while the reduced form in the presence of zinc is inactive. X-ray crystal structures of Hsp33 invariably omit details of the C-terminal domain, which is truncated in protein constructs that are capable of forming crystals.
View Article and Find Full Text PDFThe nuclear/hormone receptors are an extensive family of ligand-activated transcription factors that recognise DNA targets through a highly conserved, structurally autonomous DNA-binding domain. The compact structure of the DNA-binding domain is supported by two zinc ions, each of which is co-ordinated by the tetrahedral arrangement of thiol groups from four cysteine residues. Metal binding is expected to be linked with deprotonation of the co-ordinating thiol groups and folding of the polypeptide.
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