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The size of the rII region of bacteriophage T4

1970; Elsevier BV; Volume: 42; Issue: 3 Linguagem: Inglês

10.1016/0042-6822(70)90317-x

1096-0341

Hermann Bujard, A J Mazaitis, E. K. F. Bautz,

RNA and protein synthesis mechanisms

Heteroduplex DNA molecules featuring two loops of single-stranded DNA separated by a uniform length of double-stranded DNA were observed in electron micrographs of samples taken from annealing mixtures containing denatured DNA of selected T4 rII deletion mutants and denatured DNA of T4 DJ, a mutant with a deletion in the vicinity of the rII region between genes 39 and 56. The differences of the measured double-stranded “interloop” distances between the DJ loop and the loops caused by deletions in the rII region define the distances between the left-hand ends of the three rII deletions used, viz. r2226, r3034, and rPB296. The distance between the right-hand end of the apparently dispensable DJ region and the left hand end of the rII region is 4600 base pairs, and the estimated length of the rII region and its A and B cistrons is 2645, 1800, and 845 base pairs, respectively. The length of the deletions used was determined by measurements of the single-stranded loops. Assuming a molecular weight of 1.2 × 108 daltons for T4 DNA the rII region comprises 1.4% of the total T4 genome. The significance of these measurements with respect to the in vivo transcription of the rII region is discussed.