96-00860 Alam A basic property of living cells is their ability to respond to specific, external chemical signals and to respond appropriately. Eubacteria, like Escherichia coli and Salmonella typhimurium, respond to chemical gradients by modulating their swimming patterns towards a more favorable chemical environment. In eubacteria a family of transmembrane receptors called transducers mediate chemotaxis and some aspects of their mechanism of action is known. It is presumed that the Archaea are more closely related to eukaryotes than to eubacteria. Halobacterium salinarium, an Archaeon, responds to chemical, oxygen, and light gradients. A family of putative transducer proteins has been identified in H. salinarium using a site-specific multiple antigenic peptide antibody raised against a 23 amino acids peptide. This peptide represents a highly conserved region in eubacterial transducers. A complementary oligonucleotide probe was designed based on this conserved region and was used to select thirteen putative methyl- accepting taxis genes. Based the structural and putative functional homology with eubacterial transducers, the putative transducers fall into three structurally distinct subfamilies: a) a type with two transmembrane segments connecting large extra- and intracellular domains; b) a type with two or more transmembrane segments with an intracellular domain only; and c) a type that exists only in the cytosol as a soluble transducer. A combination of physiological, genetic, and biochemical approaches will be used to study the signal transduction mechanism of the unique transducer proteins in the Archaea H. salinarium. %%% A basic property of living cells is their ability to respond to specific, external chemical signals and respond appropriately. Eubacteria, like Escherichia coli and Salmonella typhimurium, re spond to chemical gradients by modulating their swimming patterns towards a more favorable chemical environment. In eubacteria a family of transmembrane receptors called transducers mediate chemotaxis and some aspects of their mechanism of action is known. It is presumed that the Archaea are more closely related to eukaryotes than to eubacteria. Halobacterium salinarium, an Archaeon, responds to chemical, oxygen, and light gradients. A family of putative transducer proteins has been identified in H. salinarium using a site-specific multiple antigenic peptide antibody. A combination of physiological, genetic, and biochemical approaches will be used to study the signal transduction mechanism of the unique transducer proteins in the Archaea H. salinarium. ***
