Roles of amino acid activating enzymes in cellular physiology.

INTRODUCTION ................................................................ Cellular Responses to Amino Acid Restriction.................................. Key Position ofAminoacyl sRNA Synthetases................................... MUTANTS WITH MODIFiED AMiNOACYL sRNA SYNTHETASES....................... Conditionally Expressed Mutations........................................... General background ..................................................... Temperature-conditional mutations......................................... Streptomycin-conditional mutations......................................... Methods for isolating conditional mutants.................................... Mutations Conferring Analogue Resistance.................................... Naturally Occurring Variants................................................ Epi-regulatory Mutations................................................... GENETIC AND METABOLIC CHARACTERIZATION OF MUTANTS WITH MODIFIED SYNTHETASES............................................................... Valyl sRNA Synthetase .................................................... Glycyl sRNA Synthetase ................................................... Histidyl sRNA Synthetase.................................................. Alanyl sRNA Synthetase ................................................... Arginyl sRNA Synthetase .................................................. Phenylalanyl sRNA Synthetase ............................................. PHYSIOLOGICAL RESPONSES OF MUTANTS WITH MODIFED SYNTHETASES............. Regulation ofRNA Synthesis ................................................. Regulation ofDNA Synthesis................................................ Repression ofBiosynthetic Enzzymes.......................................... End-Product Inhibition ofBiosynthetic Pathways................................ Catabolite Repression ..................................................... PHAGE-INDUCED MODIFICATION OF VALYL sRNA SYNTHETASE ACrIVITY........... SUMMARY AND FUTURE GoALS................................................. LITERATURE CITED .......................................................... 701 701 703 704 704 704 704 704 705 705 705 705