Using “Facultative Intracellular” Legionella Bacteria, Scientists Develop Unique Reversible Enzymatic Labeling System Based on a Short Peptide Sequence; Broad Potential Envisioned for Novel Approach

A research group at Umeå University in Sweden, together with researchers in Munich, Germany have identified two enzymes from the pathogenic Legionella bacteria that are very useful in chemically modifying proteins to be used in medical drugs. The result of the study is presented in the August 24, 2015 issue of the chemical journal Angewandte Chemie International Edition. The article is titled “Covalent Protein Labeling by Enzymatic Phsophocholination.” Legionella are “facultative intracellular” bacteria that use specific chemical reactions to overtake the host cell’s labeling strategy and can therefore make the cell into a suitable environment for the bacteria to multiply in. To achieve this, the bacteria pumps out various enzymes in the host cell, which act as chemical catalysts and modify the host cell’s own proteins. This leads to the proteins not being able to perform their normal tasks, and alternatively starting to perform other tasks than they were originally set out to do. Intracellular bacteria are distinct from primarily “extracellular’ bacteria, such as Staph auteus, Vibrio cholera, and Bacillus anthracis that cannot penentrate cells and that proliferate instead in the extracellular environment. One of the bacterial enzymes present in the Legionella bacteria and is called AnkX. It starts the immobilization of a small, so called phosphocholine moiety, on some of the host cell’s proteins and, further along in the course of the infection, the bacteria sends out a new enzyme, called Lem3, to remove the small moiety. At present, it is unknown why there is an enzyme that then removes the moiety from the proteins of the host cells. ”What is so interesting with the chemistry of intracellular bacteria is how it is so different in comparison to our own cell’s chemistry.
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