title: Characterization of the spoT gene of Escherichia coli.
abstract: The Escherichia coli spoT gene encodes a guanosine-3',5'-bispyrophosphate (ppGpp) 3'-pyrophosphohydrolase known to be responsible for cellular (ppGpp) degradation. The DNA sequence of the spoT region is presented. The spoT gene is deduced to be 702 codons long, with a probable UUG initiation codon, and a deduced mass of 79,342 daltons. Two spoT mutations (spoT202 and spoT203) have been localized to an open reading frame by complementation of function as well as by genetic marker rescue. The ability to overexpress the spoT gene is limited, but enough ppGppase activity can be made to reverse ppGpp accumulation during the stringent response to amino acid starvation. The spoT gene is located within a larger spo operon and is flanked by two smaller genes. The first gene in the operon encodes omega, a protein that copurifies with RNA polymerase (Gentry, D. R., and Burgess, R. R. (1986) Gene (Amst.) 48, 33-40). The spoT gene is the second gene in the operon; it is followed by a third open reading frame deduced to encode a protein with a mass of 25,343 daltons. Insertion of a kanamycin resistance gene in the omega gene reduces spoT gene expression as judged by lowered ppGppase activity, relA-dependent reduction of growth rate, and abolition of spoT mutant complementation activity. These effects are reversed by expression of the spoT gene, but not the omega gene, in trans. Transcription of the spo operon occurs in a clockwise direction on the E. coli chromosome and is probably directed by at least two promoters.
authors.affiliation: Section on Molecular Regulation, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
authors.forename: E
authors.initials: E
authors.lastname: Sarubbi
authors.forename: K E
authors.initials: KE
authors.lastname: Rudd
authors.forename: H
authors.initials: H
authors.lastname: Xiao
authors.forename: K
authors.initials: K
authors.lastname: Ikehara
authors.forename: M
authors.initials: M
authors.lastname: Kalman
authors.forename: M
authors.initials: M
authors.lastname: Cashel
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001483:Base Sequence; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000302:isolation & purification; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000302:isolation & purification; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005819:Genetic Markers; D008969:Molecular Sequence Data; D010442:Peptide Chain Initiation, Translational; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D005819:Genetic Markers; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases