Journal of Biological Chemistry
Volume 280, Issue 11, 18 March 2005, Pages 10435-10443
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Molecular Basis of Cell and Developmental Biology
A Dictyostelium Mutant with Reduced Lysozyme Levels Compensates by Increased Phagocytic Activity*

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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.

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Recipient of a Lise Meitner fellowship from Nordrhein-Westfalen.

*

This work was supported by the Deutsche Forschungsgemeinschaft Grants MA 1439/4-1 and LE 1075/2-3. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.