Lecture 3.5 Notes

Lecture 3.5 Notes - Notes Regulation of Gene...

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Notes - 3/5/10 Regulation of Gene Expression (continued) Sensing and Signal Transduction: –Chemotaxis –Control of Transcription in Archaea –Global Control and the lac Operon –The Stringent Response –Other Global Networks Regulation of Development in Model Bacteria Bacillus Caulobacter RNA-Based Regulation –Antisense RNA –Riboswitches –The trp attenuater Chemotaxis in E. coli The Sensory Receptors: Sensory proteins in the cell membrane: methyl-accepting chemotaxis proteins (MCPs) o 5 MCPs identified in E. coli, each of which can bind a variety of compounds Modified two-component regulatory system MCPs: homologous to sensor kinase family of proteins CheA/CheW: homologous to response regulator family Example: Tar transducer in E. coli responds to both attractants (aspartate and maltose) and repellants (cobalt an nickel). Response to Signal MCP cytoplasmic domain forms complex with CheW and CheA (sensor kinase) Binding of ligand affects autophosphorylation activity of CheA. o Attractants decrease activity o Repellants increase activity Interaction with flagellar motor CheA-P phosphorylates CheY (response regulator) CheY-P interacts with flagellar motor to induce clockwise rotation (tumbling) CheZ (phosphatase) dephosphorylates CheY
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•Attractant CheY-P CCW rotation (run) •Attractant CheY-P CW rotation (tumble) Adaptation MCPs affinity for ligand is altered by covalent modification (methylation). Methylation makes MCPs less responsive to attractants and more responsive repellants . Full methylation of MCPs leads to activation of CheB receptors are “reset”. Slower kinetics: initial effect on tumbling occurs in <1sec; adaptation occurs over a period of minutes. Control of Transcription in Archaea
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Lecture 3.5 Notes - Notes Regulation of Gene...

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