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Characterization of components of two amino acid transport systems of Pseudomonas aeruginosa

University of British Columbia

Isolated membranes of Pseudomonas aeruginosa were found to bind radioactive isoleucine and proline, two amino acids for which active transport systems are known. The active transport systems in whole cells of this organism are energy dependent; the binding systems in isolated membrane preparations are not energy dependent, but are inducible, require magnesium ions and are stable to short periods of sonication usually sufficient to destroy whole cells. An assay measuring the binding of radioactive amino acid to amino acid binding protein present in isolated membrane preparations of P. aeruginosa was developed and discussed. Cells induced to high levels of amino acid transport produced equivalent levels of binding on isolation of membranes from these cells. Cells repressed for amino acid transport did not lose a corresponding level of binding on isolation of their membranes, suggesting involvement of more than one protein in the active transport system of that particular amino acid. Evidence was found to substantiate claims that active transport systems are family specific, however it was also determined that the aliphatic amino acid binding system was not stereospecific. Isolated membrane preparations of P. aeruginosa were found to produce adenosine triphosphate, but this energy-rich, phosphate bond compound did not appear to function in binding of radioactive amino acid to membrane preparations. Its possible functions are discussed. Several methods of isolation of proteins with binding properties from isolated membranes and from osmotic shock supernatant fluids were attempted and discussed. There were indications of a proline binding protein present, but no evidence of an isoleucine binding protein, in the osmotic shock supernatant fluid. The isoleucine binding-protein, or proteins, appeared as an integral part of the cytoplasmic membrane. The data were discussed in an attempt to clarify the mechanism of amino acid transport in P. aeruginosa and to define the role of the amino acid binding proteins in the phenomenon of active transport.

Text

2011-05-31

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http://hdl.handle.net/2429/34997

Microbiology and Immunology

University of British Columbia

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