Uber infektiöse Substrukturen aus Escherichia coli Bakteriophagen. VIII. On the tertiary structure and biological properties of phiX174 replicative form.
As already known, phiX174 replicative-form DNA is separated into two components when sedimented in a sucrose gradient. The faster component, I, is not denatured by heat treatment, whereas the slower component, II, is converted to single strands. Only the infectivity of component II increases after heat denaturation. A quantitative comparison of data obtained by band centrifugation and by electron microscopy shows that the tertiary structure of component I is a highly twisted circle and that of component II an extended circle. By treatment with DNase, component I (as observed in band centrifugation) and twisted rings (as observed by electron microscopy) are converted at the same rate to component II and to extended circles and linear molecules. The plating efficiency of replicative-form DNA, in contrast to denatured component II replicative form and to phiX174 single-stranded DNA, is diminished by the addition of Escherichia coli DNA to the adsorption medium. The inhibition by E. coli DNA at concentrations above 0.5 microg/ml. is of first order. The lower the relative plating efficiency of native replicative-form DNA, the greater is the increase of infectivity for the denatured component II. The importance of these findings with respect to normal test conditions is discussed. Some observations suggest that under ideal test conditions the relative plating efficiency of the replicative-form DNA may rise to that of phiX174 single-stranded DNA.
Jaenisch
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Max-Planck-Institut für Biochemie, Goethestrasse 31, Munich, Germany.
Hofschneider
P H
PH
Preuss
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A
D010584:Bacteriophage phi X 174 / Q000737:chemistry / Q000235:genetics*; D002499:Centrifugation, Density Gradient; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D004279:DNA, Viral / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D004926:Escherichia coli / Q000821:virology*; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D013395:Sucrose / Q000737:chemistry
D004277:DNA, Single-Stranded; D004279:DNA, Viral; D013395:Sucrose