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Calcium Ions Are Involved In Escherichia Coli Chemotaxis, Louis S. Tisa, Julius Adler
Calcium Ions Are Involved In Escherichia Coli Chemotaxis, Louis S. Tisa, Julius Adler
Molecular, Cellular & Biomedical Sciences
Escherichia coli regulates intracellular free Ca2+ at about 90 nM [Gangola, P. & Rosen, B. P. (1987) J. Biol. Chem. 262, 12570-12574]. To increase intracellular free Ca2+, nitr-5/Ca2+, a "caged" Ca2+ compound, was electroporated into cells and then its affinity for Ca2+ was reduced by exposure to 370-nm light. Upon release of the Ca2+ ions, the cells tumbled. Studies on mutant strains showed that the receptor proteins (methyl-accepting chemotaxis proteins, MCPs) were not required for the Ca(2+)-induced tumbling but that CheA, CheW, and CheY proteins were required. Similar results were obtained with DM-nitrophen/Ca2+, another caged calcium compound that releases Ca2+ …
Membrane Topology Of The Arsb Protein, The Membrane Subunit Of An Anion-Translocating Atpase, Jianhua Wu, Louis S. Tisa, Barry P. Rosen
Membrane Topology Of The Arsb Protein, The Membrane Subunit Of An Anion-Translocating Atpase, Jianhua Wu, Louis S. Tisa, Barry P. Rosen
Molecular, Cellular & Biomedical Sciences
The ars operon of the conjugative R-factor R773 encodes an oxyanion pump that catalyzes extrusion of arsenicals from cells of Escherichia coli. The oxyanion translocation ATPase is composed of two polypeptides, the catalytic ArsA protein and the intrinsic membrane protein, ArsB. The topology of regions of the ArsB protein in the inner membrane was determined using a variety of gene fusions. Random gene fusions with lacZ and phoA were generated using transposon mutagenesis. A series of gene fusions with blaM were constructed in vitro using a beta-lactamase fusion vector. To localize individual segments of the ArsB protein, a ternary fusion …