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Z Hradecna

Publications and source records attributed to Z Hradecna.

6 recordsLinked to original sources
PubMed1990

The role of the direct repeat in qut-controlled antitermination in phage lambda.

For antitermination of transcription from the late p'R promoter of phage lambda, a cis-acting qut sequence, which overlaps with p'R, is required, together with the product of lambda gene Q. Using our BspMI-mediated multicycle technique for generation of precise deletions, we have confirmed that deletions removing DNA downstream of +18 bp (counted from the p'R-controlled transcriptional start point s'R = +1) do not affect the efficiency of qut antitermination; at the same time we found that deleting one more bp (shifting the right-hand boundary to bp +17) reduces antitermination by only 20%. Deleting another 5 or 6 bp (+11 or +12 bp right-hand qut boundary), decreases antitermination by about 80%. These deletions reduce the 9/10-bp-direct repeat (5'-TGGGT(A or T)AATT)2 in qut to only the five italicized bp. Similar strong reduction in antitermination (by about 68%) was obtained with +16 bp qut boundaries, in constructs which also contained 2- or 3-bp insertions between bp +11 and +12 or between +12 and +13. Since the latter deletions retain only 5/10 bp of the direct repeat, it appears that antitermination is dependent on the length and intactness of the direct repeat.

Bacteriophage lambda↗
PubMed1975

Photobiological behaviour of bacteria and phages supplemented with aza-analogoues of nucleic acid bases.

The photochemical stability of anomalous nucleic acid bases of the azatype, 5-azacytosine (I), 5-azacytidine (II), 6-azacytosine (III), 6-azacytidine (IV), 6-azathymine (V), 6-azauracil (VI), and 8-aza-adenine (VII) to U. V. light of the wavelength 254 nm differs from the U. V. stability of the normal constituents. Changes of the U.V. inactivation of Escherichia coli K12 C600, E. coli B, Bacillus cereus, as well as E. coli phages gamma cb2 and gamma b2b5 supplemented with azaderivatives prior to irradiation were investigated. It was found that I, II, III, IV, and VII are more, V and VI less sensitive to U. V. light compared with corresponding natural nucleic acid bases. Their changed U. V. sensitivities are reflected in the survival curves after U. V. -irradiation in as far as azabases are incorporated into the nucleic acids in vivo. This explains the increase in U.V. sensitivity of E. coli K12 C600, E. coli B, and B. cereus supplemented with I, II, III, IV, and VII and the decrease in U.V. sensitivity of Streptococcus faecalis supplemented with V (the latter information was taken from Gunther and Prusoff 1967). The lack of any significant influence on inactivation curves of E. coli K12 C600 by V and VI, and on E. coli phages gamma cb2 and gamma c2b5 by II, is discussed in terms of too small incorporation rates. No discrimination was put forward with respect to DNA and RNA incorporation.

Adenine↗