A Dictyostelium mutant with reduced lysozyme levels compensates by increased phagocytic activity.
Lysozymes are bacteria-degrading enzymes and play a major role in the immune defense of animals. In free-living protozoa, lysozyme-like proteins are involved in the digestion of phagocytosed bacteria. Here, we purified a protein with lysozyme activity from Dictyostelium amoebae, which constitutes the founding member, a novel class of lysozymes. By tagging the protein with green fluorescent protein or the Myc epitope, a new type of lysozyme-containing vesicle was identified that was devoid of other known lysosomal enzymes. The most highly expressed isoform, encoded by the alyA gene, was knocked out by homologous recombination. The mutant cells had greatly reduced enzymatic activity and grew inefficiently when bacteria were the sole food source. Over time the mutant gained the ability to internalize bacteria more efficiently, so that the defect in digestion was compensated by increased uptake of food particles.
Müller
Iris
I
Department of Cell Biology, Kassel University, Heinrich-Plett-Strasse 40, 34132 Kassel, Germany.
Subert
Ninon
N
Otto
Heike
H
Herbst
Rosa
R
Rühling
Harald
H
Maniak
Markus
M
Leippe
Matthias
M
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D019992:Databases as Topic; D004023:Dictyostelium / Q000378:metabolism*; D004705:Endocytosis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D016296:Mutagenesis; D009154:Mutation; D010587:Phagocytosis; D010641:Phenotype; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid
D000939:Epitopes; D016271:Proto-Oncogene Proteins c-myc; D049452:Green Fluorescent Proteins; D009113:Muramidase