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L Haarr

Publications and source records attributed to L Haarr.

43 records · Page 3Linked to original sources
PubMed1980

DNA-RNA polymerase complexes associated with the membrane from bacteriophage T2- or T4-infected Escherichia coli. I. General properties.

Properties of DNA-RNA polymerase complexes, apparently bound to a fraction of the cell membrane of bacteriophage T2- or T4-infected Escherichia coli, are described. Evidence is presented to show that the complexes initiate the asymmetric synthesis of RNA, and release the finished product. The transcription capacity per unit of beta' + beta was 10 times higher at 6 min than at 30 min after infection.

Cell Membrane↗
PubMed1980

DNA-RNA polymerase complexes associated with the membrane from bacteriophage T2- or T4-infected Escherichia coli. II. A comparison of in vitro RNA with the in vivo RNA products.

Membrane preparations, containing DNA-RNA polymerase from bacteriophage T2- or T4-infected Escherichia coli, caused the asymmetric synthesis of RNA classes similar to those produced sequentially in vivo: 1, Pre-early RNA was formed when a membrane preparation was isolated 1 min after infection. 2, Pre-early and delayed early RNA, in roughly the same proportion as that obtained in vivo, was synthesized by a preparation obtained 6 min after infection. 3, Pre-early, delayed early and late genes were transcribed by preparations isolated from cells during the late period of infection. In late preparations, however, less late and more pre-early RNA was usually synthesized in vitro than that obtained in vivo. Late RNA was not synthesized when a phage T4 mutant defective in either gene 33 or gene 55 was used. Evidence is presented to show that late RNA synthesis cannot solely be accounted for from the completion of already initiated chains.

Cell Membrane↗
PubMed1976

Conversion of Escherichia coli RNA polymerase to a template independent enzyme.

Preparations of RNA polymerase (E.C.2.7.7.6) from uninfected Escherichia coli, T4 infected Escherichia coli, and Acinetobacter calcoaceticus when centrifuged in sucrose gradients in the absence of magnesium ions gave rise to five peaks, all of which were able to form polymers from ribonucleoside 5'-triphosphates in the absence of template or primer. All of the peaks obtained from the Escherichia coli enzyme appeared to contain the subunit alpha and beta and, in addition, polypeptides which appeared to be derived from the subunit beta.

Acinetobacter↗
PubMedDate not supplied

Role of penicillin-binding protein 5 C-terminal amino acid substitutions in conferring ampicillin resistance in Norwegian clinical strains of Enterococcus faecium.

The importance of amino acid sequence differences in the C-terminal part and levels of mRNA expression of penicillin-binding protein 5 (PBP5) for ampicillin resistance in Enterococcus faecium was investigated. Seventeen isolates from Norwegian hospitalized patients (ampicillin MIC 0.064->256 mg/L) with different C-terminal pbp5 DNA sequences encoding 11 different amino acid sequences were analyzed with a 14C-radiolabeled penicillin- binding assay to PBP5 and with real-time PCR quantification of pbp5 mRNA expression. Using multiple logistic regression analysis the amino acid substitution Met 485 was linked to ampicillin MIC and levels of 14C-radiolabeled penicillin bound to PBP5; however, there were isolates with identical PBP5 alleles and different ampicillin MICs. There was no relation between the quantity of pbp5 mRNA transcripts and ampicillin resistance. The results cannot explain ampicillin resistance in Norwegian clinical strains of E. faecium and indicate that other factors besides the properties of the C-terminal part of PBP5 are most likely involved.

Amino Acid Substitution↗