Recombinant Dictyostelium discoideum Probable T4-type lysozyme 2 (DDB_G0274291)
Description
Introduction
Dictyostelium discoideum, a social amoeba, exhibits a unique life cycle involving aggregation and fruiting body formation, which requires a soluble counting factor (CF) . The CF complex, crucial for group size determination, includes proteins like CF45-1 and CF50 . These proteins show sequence similarities to Chalaropsis- and Entamoeba-type lysozymes, though their enzymatic activity was unconfirmed until recently . D. discoideum also serves as a model to study unicellular traits, such as motility, chemotaxis, and phagocytosis .
Molecular Characterization of CF Lysozymes
CF lysozymes possess an N-terminal glycoside hydrolase family 25 (GH25) domain and a C-terminal low-complexity region rich in serine, glycine, alanine, and asparagine residues . Research has demonstrated the enzymatic activity of recombinant CF lysozymes, particularly CF50 . A truncated CF50 version, lacking the C-terminal region, showed significantly enhanced lysozyme activity .
Enzymatic Properties
CF lysozymes exhibit strict pH dependence, with maximal activity at pH 3.0-3.5 under acidic conditions . They are most active at low ionic strengths and stable only at relatively low temperatures . Site-directed mutagenesis has identified a crucial glutamic acid residue essential for catalysis, suggesting a neighboring group catalytic mechanism similar to other GH25 lysozymes .
Role in Cell-Cell Adhesion and Motility
Cell-cell adhesion, regulated by CF, influences group size in D. discoideum . CF decreases group size by increasing polymerized actin (F-actin) and decreasing assembled myosin II, thereby enhancing cell motility . CF potentiates cAMP-stimulated activation and translocation of Akt/protein kinase B (Akt/PKB), which activates PAKa to regulate myosin II heavy chain phosphorylation and assembly, increasing cell motility .
Bacteriolytic Activity
D. discoideum exhibits bacteriolytic activity against K. pneumoniae, mimicking the destruction of ingested bacteria in phagosomes, which is most efficient against bacteria with disrupted cell walls . This activity is observed at very acidic pH (approximately pH 2), similar to conditions in D. discoideum endosomes and phagosomes . Mutant K. pneumoniae waaQ bacteria are lysed more efficiently than parental strains, and the bacteriolytic activity is lower in kil1 knockout (KO) cells .
T4 Lysozyme and Folding Pathway
T4 lysozyme, unrelated to CF lysozymes, has been extensively studied for its structure and folding . It consists of two energetically coupled domains: N- and C-terminal . The folding pathway of T4 lysozyme involves a hidden intermediate with a largely native-like structure .
Data Representation
| Feature | CF Lysozymes | T4 Lysozyme |
|---|---|---|
| Structure | GH25 domain, C-terminal low-complexity region | N- and C-terminal domains |
| Activity | pH dependent, active under acidic conditions | |
| Function | Group size determination, cell-cell adhesion, cell motility | |
| Organism | Dictyostelium discoideum | Bacteriophage T4 |
| Key residues for catalysis | Glutamic acid |
Product Specs
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