Sensory Transduction in Archaea

Alam, Maqsudul

Abstract

THIS IS A SHANNON AWARD PROVIDING PARTIAL SUPPORT FOR THE RESEARCH PROJECTS THAT FALL SHORT OF THE ASSIGNED INSTITUTE'S FUNDING RANGE BUT ARE IN THE MARGIN OF EXCELLENCE. THE SHANNON AWARD IS INTENDED TO PROVIDE SUPPORT TO TEST THE FEASIBILITY OF THE APPROACH; DEVELOP FURTHER TESTS AND REFINE RESEARCH TECHNIQUES; PERFORM SECONDARY ANALYSIS OR AVAILABLE DATA SETS; OR CONDUCT DISCRETE PROJECTS THAT CAN DEMONSTRATE THE PI'S RESEARCH CAPABILITIES OR LEND ADDITIONAL WEIGHT TO AN ALREADY MERITORIOUS APPLICATION. THE ABSTRACT BELOW IS TAKEN FROM THE ORIGINAL DOCUMENT SUBMITTED BY THE PRINCIPAL INVESTIGATOR. DESCRIPTION: Recent progress in phylogenetic research demonstrated that the Archaea are more closely related in eukaryotes than to eubacteria. Halobacterium salinarium, a member of Archaea responds to changes in chemical environment, oxygen and reacts to light. Central to the system is a family of transmembrane receptors, called transducers. Recently we have identified a large family of transducer proteins from the Archaeon H. salinarium. Eleven putative transducer genes have been cloned. The Kyte-Doolitile hydropathy plots of the four newly identified transducer proteins reveal an interesting feature not common in eubacteria. Two of them do not contain any transmembrane segment indicating a new type of soluble transducer proteins. We have also demonstrated that methylation and demethylation are also involved in Osmotaxis. The pattern of altered release of volatile methyl groups upon sensory stimulation of H. salinarium exhibits a puzzling asymmetry. The positive and the negative stimulation by chemicals, oxygen, osmotic agents or light result in increased release. This is unlike Escherichia coli in which positive stimuli lower the rate of methanol release and negative stimuli increase it. The origin of this asymmetry is not understood. This proposal involves physiological, genetic and biochemical approaches to the study of signal transduction in Archaeon H. salinarium. We will determine the physiological function of transducer proteins by creating deletion mutants of appropriate transducer genes. We will develop high- expression vectors to purify sufficient amounts of recombinant transducer proteins for immunological studies. We will identify eubacterial Che homologs in Archaea. We will determine why positive and negative stimulation by chemicals, oxygen, osmotic agents and light result in increase release of methanol, exhibiting a puzzling asymmetry unlike in eubacteria. We will also study the possible function of methylation in excitation signal, which may reveal insight in molecular signaling pathways that are not utilized by eubacteria.