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D L Miller

Publications and source records attributed to D L Miller.

At least 433 records · Page 24Linked to original sources
PubMed1981

Discrimination between D- and L-tyrosyl transfer ribonucleic acids in peptide chain elongation.

D-Tyr-tRNA can take part in peptide bond formation with N-AcPhe-tRNA on ribosomes programmed with the hexanucleotide UUUUAC. None of the steps leading to peptide bond formation exhibit high stereoselectivity. Ternary complex formation with EF-Tu.GTP favors L-Tyr-tRNA by a factor greater than 25. The complex formed with D-Tyr-tRNA was not protected from hydrolysis, which suggests that the D-amino acid is improperly bound to the protein. The rate of EF-Tu-promoted dipeptide formation was 30-fold faster with L-Tyr-tRNA. The ratio of moles of GTP hydrolyzed to dipeptide formed was 1.4 for L-Tyr-tRNA and 4 for D-Tyr-tRNA. The excess of GTP hydrolyzed to peptide bonds formed is evidence for kinetic proofreading in AA-tRNA selection. The combined effects of the partial discrimination at each stage, from the aminoacylation to the peptide formation, favor L-tyrosine by a factor greater than 10(4) and would virtually exclude D-tyrosine from being incorporated under conditions where L-tyrosine was also present.

Escherichia coli↗
PubMed1981

A mutation in the tRNAAsp gene from yeast mitochondria. Effects on RNA and protein synthesis.

We have characterized a mutation that affects the tRNAAsp coded by yeast mitochondrial DNA. Comparison of the DNA sequences of the tRNAAsp gene from a wild type strain and the mutant demonstrates that the mutant differs by a C to U base change in position 72 of the tRNA. This mutation abolishes mitochondrial protein synthesis, presumably because the tRNAAsp made from this gene cannot be charged with aspartic acid (FAye, G., Bolotin-Fukuhara, M., and Fukuhara, H. (1976) in The Genetics and Biogenesis of Chloroplasts and Mitochondria (Bucher, C. T., Neupert, W., Sebalt, W., and Werner, S., eds) pp. 547-555, North Holland Publishing Co., Amsterdam). It also reduces the amount of tRNAAsp transcripts in the mutant as compared to the wild type.

Base Sequence↗
PubMed1981

Effect of transfer ribonucleic acid dimer formation on polyphenylalanine biosynthesis.

Escherichia coli tRNAPhe (anticodon GAA) as well as yeast tRNAPhe (anticodon GmAA) forms a strong complex with E. coli tRNAGlu (anticodon s2UUC) through an interaction between their complementary anticodons. This interaction inhibits aminocylation of tRNAPhe but not the formation of a complex with elongation factor Tu. Moreover, at 0 degrees C, tRNAGlu strongly inhibits the binding of Phe-tRNA to poly(U)-programmed ribosomes via either the enzymic (EF-Tu-promoted) or nonenzymic pathway. At 15 degrees C, tRNAGlu effectively inhibits polyphenylanine synthesis in the E. coli system. The inhibition is reversed at 37 degrees C, where the Phe-tRNA.tRNAGlu dimer is dissociated. Calculations based upon the E. coli intracellular concentrations of tRNAs and the published rates of association and dissociation of the tRNA dimers suggest that this interaction may inhibit protein synthesis in vivo at temperatures below 15 degrees C.

Anticodon↗
PubMed1981

Survey of antibiotic prescribing in a district general hospital. III. Urinary tract infection.

A 28 day survey of all antibiotic prescriptions in a district general hospital included a brief interview with the prescriber of each prescription. Fifty-nine antibiotic courses were stated by the prescriber to be for the treatment of urinary tract infection (UTI). Urine specimens from all patients treated for UTI were sent to the laboratory for bacteriological examination. 29 patients' treatment was started as the result of isolation of bacteria from the urine. 20 of the patients also had symptoms suggestive of UTI. 4 patients were treated solely because bacteria had been isolated from "routine" catheter stream urine specimens. 7 patients were treated for UTI despite the availability, at the time of prescription, of a laboratory report stating that bacteria had not been isolated from the urine. 19 patients' treatment was started before the results of bacteriological tests were available. By combining information about bacteriological examination of the urine specimens and clinical details recorded during the interview with the prescribed, it was considered that both initiation and continuation of antibiotic treatment was justified for 28/55 patients and that either initiation or continuation of treatment was unjustified for 27/55 patients.

Anti-Bacterial Agents↗
PubMed1981

Survey of antibiotic prescribing in a district general hospital. II. Lower respiratory tract infection.

A 28 day survey of all antibiotic prescriptions in a district general hospital included a brief interview with the prescriber of each prescription. One hundred and nineteen antibiotic courses were stated, by the prescriber, to be for the treatment of lower respiratory tract infection. By combining the prescriber's clinical evidence, laboratory data, and radiographic findings, an "index of infection" was produced for 94 patients. This index reflected features associated with bacterial infection of the lower respiratory tract and suggested that 49% of the antibiotic courses prescribed were justifiable, 11% were questionable, and 40% were unjustifiable. The choice of antibiotic was usually appropriate to the prescriber's diagnosis. Over 80% of the antibiotics used were of the penicillin group. Ampicillin, the single most frequently prescribed drug, accounted for 60% of the prescriptions. The frequency of diagnosis of chest infection increased with age. Almost 40% of patients over 81 years old who were admitted to hospital during the survey were prescribed antibiotics for chest infection. A higher proportion of older than of younger patients had low indices of infection.

Adolescent↗
PubMed1981

Survey of antibiotic prescribing in a district general hospital. I. Pattern of use.

In a survey of all antibiotic prescription in a district general hospital during November, 1978, the reason for each prescription was determined by a brief interview with the prescriber. 28% of all inpatients received antibiotics. Older patients were prescribed antibiotics more often than were younger patients. Ampicillin was the most frequently used antibiotic, accounting for over 40% of prescriptions. Over 70% of antibiotic courses were stated by the prescriber as being for the treatment of infection and the remainder were said to be prophylactic. Although 80% of the antibiotics were assessed as suitable treatment for the stated infection, most of the patients were treated without bacteriological evidence of the infecting agent and, for these patients, prescribers were unable to specify the pathogen against which treatment was intended in 50% of the courses they initiated. Only 7% of antibiotics prescribed for conventional surgical prophylaxis fulfilled all the criteria used to assess the suitability of choice of drug and the method and timing of its administration.

Adolescent↗
PubMed1981

The amino acid sequence of elongation factor Tu of Escherichia coli. The complete sequence.

The complete amino acid sequence of elongation factor Tu of Escherichia coli has been established by sequencing overlapping cyanogen bromide and tryptic peptides. Sequence analysis of peptides was done primarily by solid-phase Edman degradation. Elongation factor Tu is a single chain polypeptide composed of 393 amino acids (Mr = 43,225). Its NH2 terminus is blocked with an acetyl group, as determined by mass spectroscopy, and lysine 56 is partially methylated. The cysteine residues associated with aminoacyl tRNA and guanosine nucleotide binding are located at positions 81 and 137, respectively. Although elongation factor Tu is coded for by two genes, the only site of microheterogeneity found was at the carboxyl terminus (residue 393), which is either glycine or serine. Comparison of the first 140 amino acids of elongation factor Tu and of elongation factor G shows a strong (31%) sequence homology. In addition, secondary structure calculations predict remarkable conformational similarities between the two proteins. The NH2-terminal region of elongation factor Tu appears to be composed of two beta-sheet domains connected by an exposed, alpha-helical bridge, which includes a 14-amino acid segment released by limited treatment with trypsin. Structural features of the aminoacyl-tRNA binding site are discussed in the light of sequence and other chemical and biochemical data.

Amino Acid Sequence↗
PubMed1981

Identification of a histidine residue near the aminoacyl transfer ribonucleic acid binding site of elongation factor Tu.

The complex of elongation factor Tu with GTP (EF-Tu.GTP) reacts with N or epsilon -bromoacetyl-lys-tRNA ( or epsilon BrAcLys-tRNA) to form a functional covalently linked complex (XLTC). The site of cross-linking must be near the site on EF-Tu.GTP that binds the aminoacyl moiety of aminoacyl transfer ribonucleic acid (AA-tRNA). For identification of this site, a nanomole of purified XLTC prepared from or epsilon BrAc[(14)C]Lys-tRNA was digested first with RNase A and then with trypsin, and the peptides were resolved by high-performance liquid chromatography using a c8 reverse-phase column. A single peptide contained 80% of the label. The amino acid composition of this peptide was identical with that of residues 59-74 in EF-Tu. The NH2-terminal sequence of the peptide was determined to be Fly-Ile-Thr-Ile, which are residues 59-62 in EF-Tu. The modified amino acid was identified as pi - (carboxymethyl)histidine, which establishes that His-66 is at or near the AA-tRNA binding site on EF-Tu.GTP.

Affinity Labels↗
PubMed1981

Transfer RNA cross-linked to the elongation factor Tu subunit of Q beta replicase does not inhibit Q beta RNA replication.

One of the four subunits of bacteriophage Q beta RNA replicase is elongation factor Tu (EF-Tu), the host aminoacyl-tRNA (AA-tRNA) binding protein. To determine whether the RNA polymerase activity requires the tRNA binding site of EF-Tu, we reconstituted replicase with EF-Tu . GTP covalently bound to AA-tRNA. This cross-linked ternary complex (XLTC) was formed by the reaction of N epsilon-bromoacetyl-Lys-tRNA with EF-Tu-GTP. In an EF-Tu-dependent system for the reconstitution of replicase, XLTC restored polymerase activity at least as well as an equivalent amount of EF-Tu. Replicase reconstituted with XLTC was resolved from replicase containing EF-Tu by chromatography on phosphocellulose, a result which confirmed that the tRNA moiety was incorporated into the enzyme. Chromatographic analysis of reconstitution mixtures revealed that XLTC was incorporated into replicase as extensively as EF-Tu. From these results, it appears that the AA-tRNA binding site on EF-Tu is not required for the assembly or activity of Q beta RNA replicase. Furthermore, because the tRNA macromolecule is cross-linked to His-66 of the EF-Tu, the region surrounding His-66 must normally be exposed on the surface of the replicase.

Bacterial Proteins↗
PubMed1981

Pertussis immunisation and serious acute neurological illness in children.

The first 1000 cases notified to the National Childhood Encephalopathy Study were analysed. The diagnoses included encephalitis/encephalopathy, prolonged convulsions, infantile spasms, and Reye's syndrome. Eighty-eight of the children had had a recent infectious disease, including 19 with pertussis. Only 35 of the notified children (3.5%) had received pertussis antigen within seven days before becoming ill. Of 1955 control children matched for age, sex, and area of residence, 34 (1.7%) had been immunised with pertussis vaccine within the seven days before the date on which they became of the same age as the corresponding notified child. The relative risk of a notified child having had pertussis immunisation within that time interval was 2.4 (p less than 0.001). Of the 35 notified children, 32 had no previous neurological abnormality. A year later two had died, nine had developmental retardation, and 21 were normal. A significance association was shown between serious neurological illness and pertussis vaccine, though cases were few and most children recovered completely.

Acute Disease↗
PubMed1981

Interaction of elongation factor Tu with the aminoacyl transfer ribonucleic acid dimer Phe-tRNA-Glu-tRNA.

The effect of EF-Tu.GTP on the codon-anticodon interaction of AA-tRNA was studied by using as a model system the interaction of AA-tRNAs with complementary anticodons, namely, dimerization between yeast or Escherichia coli Phe-tRNAPhe (anticodon GmAA) and E. coli Glu-tRNAGlu (anticodon s2UUC) or nonacylated tRNAGlu in the presence or absence of EF-Tu.GTP. The present data indicate that the ternary complexes Phe-tRNA-EF-Tu.GTP and Glu-tRNA-EF-Tu.GTP can form dimers with a binding constant of (0.9 +/- 0.2) X 10(6) M-1, which is identical in magnitude with that of the dimer of the nonacylated tRNAs tRNAPhe-tRNAGlu and also with that of the complex Phe-tRNA-EF-Tu.GTP with nonacylated tRNAGlu. These results show that the anticodon region is not affected by complexation with EF-Tu.GTP; however, this conclusion does not preclude the possibility of structural changes in the anticodon loop that have no effect in energetic terms. In addition, this model codon-anticodon interaction does not stimulate hydrolysis of the GTP bound in the ternary complex.

Anticodon↗
PubMed1981

Giant Meckel's diverticulum. A cause of intestinal obstruction.

Giant Meckel's diverticula are more likely to cause obstruction than bleeding. In neonates, this is commonly due to volvulus; in adults, it is usually due to adhesions and a mass effect. A lateral view of the abdomen following barium studies can be helpful. This entity should be included in the differential diagnosis of intestinal obstruction, especially incomplete, intermittent, and chronic forms.

Colonic Diseases↗
PubMed1981

Alpha-aminoisobutyric acid loss by rat small intestine: role of intestinal site and luminal contents.

Loss of amino acid into the lumen may be important in diarrheal states. Labeled alpha-aminoisobutyric acid (AIB) was given parenterally, and concentration gradients developed between lumen, intestinal tissue and plasma. After 24 h, we measured AIB loss into the intestinal lumen by recirculating isolated segments in situ under conditions of either net water absorption or net water secretion. Final 14C-AIB concentrations in intestinal tissue were 200-800 times that of lumen, 6--15 times that of serum. Despite increased total 14C-AIB loss during net water secretion, and based on the low luminal 14C-AIB concentrations, the contribution of amino acid loss to fecal nitrogen during osmotic diarrhea appears to be minimal.

Aminoisobutyric Acids↗