Receptor structure in the bacterial sensing system.

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Abstract
The primary receptors for aspartate and serine in bacterial chemotaxes are the 60,000 dalton proteins encoded by the tar and tsr genes. The evidence is: overproduction of the tar gene product at various levels by recombinant DNA techniques produces proportionate increases in aspartate binding; aspartate binding copurifies with [3H]methyl-labeled tar gene product; antibody to tar and tsr protein fragments precipitates a single species of protein (60,000 daltons) which retains binding capacity and [3H]carboxymethyl label. Partially purified tar gene product can be reconstituted into artificial vesicles and retains aspartate binding and aspartate-sensitive methylation and demethylation. The aspartate and serine receptors are transmembrane proteins of a single polypeptide chain with the receptor recognition on the outside of the membrane and the covalent methylation site on the inside.