TY - JOUR
T1 - Kinetics and intermediates in the intracellular synthesis of bacteriophage T4 deoxyribonucleic acid
AU - Altman, Sidney
AU - Lerman, L. S.
N1 - Funding Information:
We m grateful to Dr A. B. Brill of the Vanderbilt University School of Medicine for saplea of various radio-opaque agents, of which sodium iothalamate was found to be innocuous to T4. During most of the period of this work one of ~FJ( S.A.) was & University Fellow of the Univereity of Colordo, asld the work was begun in the Department of Biophysics of the University of Colorado School of Medicine. This research was supported by grant no. GM13767 from the National Institutes of Health and by granf no. GB4119 from the National Science Foundation.
PY - 1970/6/14
Y1 - 1970/6/14
N2 - 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.
AB - 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.
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U2 - 10.1016/0022-2836(70)90190-7
DO - 10.1016/0022-2836(70)90190-7
M3 - Article
C2 - 5476915
AN - SCOPUS:0014945040
SN - 0022-2836
VL - 50
SP - 235
EP - 261
JO - Journal of molecular biology
JF - Journal of molecular biology
IS - 2
ER -