Kinetics and intermediates in the intracellular synthesis of bacteriophage T4 deoxyribonucleic acid

Sidney Altman, L. S. Lerman

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


A kinetic model of bacteriophage T4 DNA replication is described in which the first stages are identified with two DNA-containing particles resolvable by velocity sedimentation. The first stage is a complex of DNA and protein and appears to include cell membrane fragments. DNA from infecting phage rapidly enters this complex. The second intermediate sediments more rapidly than is expected from its molecular weight assuming that the molecule is linear. Since no more than 4% by weight of this intermediate is protein, RNA or denatured regions, these factors cannot account for the high sedimentation coefficient. There are no closed covalent circles in the second intermediate, and in alkali, no single strands of length greater than two single-stranded equivalents of T4 DNA are detectable. If it is asssumed that the second intermediate is a highly branched or looped molecule rather than a linear one, the discrepancy between the observed and expected sedimentation coefficients is much reduced,. A formal analysis of pulse-labeling experiments indicates that part of the DNA in the replicating pool differs from the remainder in a way that precludes its loss from the pool. That is, a conserved section of the pool of replicating DNA exists which may constitute a template for further DNA replication. The last stages in the maturation scheme are identified with 60 s DNA resembling the DNA extracted from T4 particles and with mature phage particles. The bulk of the 60 s DNA is not a precursor for phage particles.

Original languageEnglish (US)
Pages (from-to)235-261
Number of pages27
JournalJournal of molecular biology
Issue number2
StatePublished - Jun 14 1970
Externally publishedYes

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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