Linked Life Data

3112412

Source:http://linkedlifedata.com/resource/pubmed/id/3112412

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1987-9-2
pubmed:databankReference
pubmed:abstractText
Expression of the threonine (thr) operon enzymes of Escherichia coli is regulated by an attenuation mechanism. The regulatory portion of the operon contains a region coding for a leader peptide that contains consecutive threonine and isoleucine codons. It is thought that translation of the leader peptide controls the frequency of transcription termination at the attenuator site. Using oligonucleotide-directed site-specific mutagenesis we have altered the putative control codons of the leader peptide coding region. In two of the mutants the threonine and isoleucine codons were changed to produce peptides containing histidine and tyrosine codons. Both mutants showed loss of regulation by threonine and isoleucine. A hisT mutation, which leads to an undermodification of tRNA(His), increased thr operon expression in the mutants threefold but did not affect expression of the wild-type thr operon. Two other mutants were constructed that contained two histidine codons early in the leader peptide. Expression in both of these mutants was unaltered by the presence of the hisT allele or by the addition of threonine and isoleucine to the growth medium. In addition, a wild-type strain containing a temperature-sensitive threonyl-tRNA synthetase mutation showed increased thr operon expression at the non-permissive temperature, whereas none of the mutants showed any change. Taken together these data indicate that the specificity of the attenuation response is effected by specific control codons within the thr leader peptide coding region. We have also directly demonstrated thr leader peptide synthesis in vitro using a plasmid encoding the wild-type thr leader region to direct the synthesis of a peptide of the appropriate molecular weight when labeled with [3H]threonine but not with [3H]histidine or [3H]tyrosine. Conversely, when extracts were incubated with templates containing the mutated DNAs, peptides were labeled that showed patterns consistent with the expected amino acid compositions. These data indicate that the thr leader RNA is translated into the predicted leader peptide.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
194
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
59-69
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1987
pubmed:articleTitle
Specificity of the attenuation response of the threonine operon of Escherichia coli is determined by the threonine and isoleucine codons in the leader transcript.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.