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Biomedical subjects

C Squires

Publications and source records attributed to C Squires.

52 records · Page 3Linked to original sources
PubMed1976

Nucleotide sequence of region preceding trp mRNA initiation site and its role in promoter and operator function.

The nucleotide sequence of the region preceding the transcription initiation site of the tryptophan operon of Escherichia coli was determined. Essentially all of the trp operator precedes the transcribed portion of the operon. The deduced sequence contains the recognition site of endonuclease Hpa I. This site is protected from Hpa I cleavage by RNA polymerase and by trp repressor. Regions of 2-fold symmetry are present in the DNA sequence.

Base Sequence↗
PubMed1973

Three adjacent transfer RNA genes in Escherichia coli.

A defective varphi80 transducing phage has been isolated that carries a small section of the E. coli chromosome from the region near argH (77 min). This phage contains three E. coli tRNA genes, termed glyTsu(+) (36), tyrT, and thrT. These genes specify the structures of tRNA(2) (Gly) (su(+) (36)) tRNA(2) (Tyr), and tRNA(3) (Thr), respectively. Induction of a single lysogen bearing this phage brings about selective synthesis and amplification of only these three tRNAs.

Amino Acids↗
PubMed1973

Nucleotide sequences from tryptophan messenger RNA of Escherichia coli: the sequence corresponding to the amino-terminal region of the first polypeptide specified by the operon.

Mutants with internal deletions that terminate near the operator end of the tryptophan operon of E. coli were used in studies on the nucleotide sequence at the 5' end of the messenger RNA transcribed on this operon. The findings obtained permitted identification of a sequence of 43 nucleotides corresponding to the aminoterminal 11 amino acids of anthranilate synthetase component I, the polypeptide specified by the operator-proximal structural gene of the operon. It was also shown that the translation initiation codon for this polypeptide is preceded on the messenger by a "leader" sequence of unknown function, at least 150 nucleotides in length.

Amino Acid Sequence↗
PubMed1969

The L-arabinose operon in Escherichia coli B-r: a genetic demonstration of two functional states of the product of a regulator gene.

The product of the regulator gene araC in the L-arabinose gene complex exists in two functional states: P1, the repressor, and P2, the activator, presumably in equilibrium with each other, and with P1 and P2 attached to their respective controlling sites, araO, the operator, and araI, the initiator. The controlling sites are linked in the following order with respect to genes araB and araC: BIOC. Two C gene deletions (Delta719 and Delta766) serve to define the newly described araO site, and to place it adjacent to the left end of the C gene. We have suggested that deletion 719 deletes, in addition to the C gene, part or all of the araO site. Deletion 766 leaves the araO site intact. Complementation analysis employing stable merodiploids indicates that the repressor-operator site function is epistatic over the activator-initiator site function. It is necessary both for activator (P2) to be present and for repressor (P1) to be absent at their respective controlling sites (araI and araO) for full expression of the L-arabinose operon.

Arabinose↗
PubMedDate not supplied

The gastrointestinal absorption of methadone in the rat.

The absorption of dl-methadone from the gastrointestinal tract of the Sprague-Dawley rat was examined by the in vivo segment technique. Duodenal absorption, measured as a function of time and dose, followed first-order kinetics with a half-life of 15.6 min. Absorption was not influenced by prior or concomitant administration of a variety of drugs. Absorption from other regions of the intestine was similar to that from the duodenum; in contrast, absorption from the stomach was markedly slower. Gastric absorption was increased by alkalinization of stomach contents but was still considerably slower than from the duodenum. Gastric emptying of methadone appears to be the rate-limiting step in the overall gastrointestinal absorption of the drug, since the rate of emptying following intubation of the drug into the stomach was also considerably slower than the rate of duodenal absorption.

Animals↗