Jazwinski, S. M., R. Marco, and A. Kornberg. 1975. The gene H spike protein
of bacteriophages phiX174 and S13. II. Relation to synthesis of the parental
replicative form. Virology 66:294-305.
Several molecules of the phiX174 gene H protein, a component of the phage spike, become
firmly associated with the host cell upon infection and resist protease treatment of the cell. The
gene H protein was recovered in association with the phage DNA converted to the duplex
replicative form and was bound to several different regions of the DNA. Similar results were
obtained with the gene H protein of the related phage S13. Cells infected with a temperaturesensitive mutant of S13 in gene H failed to make parental replicative form at the restrictive
temperature, although phage binding and eclipse occurred at normal levels. Since phage
penetration is coupled to replication and the gene H protein is recovered tightly bound to the
parental replicative form, this protein is presumed to participate in the first stage of DNA
synthesis. These and related findings form the basis for a general proposal of a “pilot protein” as
a minor component of the virus with multiple functions in adsorption, penetration, and early
intracellular stages of viral chromosome expression.
Jazwinski, S. M., A. A. Lindberg, and A. Kornberg. 1975. The gene H spike
protein of bacteriophages phiX174 and S13. I. Functions in phage-receptor
recognition and in transfection. Virology 66:283-93.
The gene H protein of bacteriophage phiX174 is a coat component located in the spikes at the
vertices of the polyhedron. In phiX174-infected cells, the gene H protein binds to exogenous
single-stranded phage DNA enhancing its infectivity in transfection of spheroplasts. This
stimulation was not observed with extracts deficient in gene H protein. Transfection by the gene
H protein-DNA complex was specifically inhibited by antibody to gene H protein.
Lipopolysaccharide derived from phiX174-sensitive cells blocked transfection by the DNA
complex with gene H protein but not by the DNA alone, suggesting that the gene H protein
functions as the phage adsorption protein by recognizing the phage lipopolysaccharide receptor.
Gene H protein from phiX174 stimulated the transfection by single-stranded DNA from the
closely related phage S13; this stimulation was blocked by antibody to gene H protein and by the
phiX174 lipopolysaccharide receptor. These actions in phage-receptor recognition and in
transfection suggest that the gene H protein has multiple functions and behaves as a “pilot
protein” in guiding the phage and its DNA through several stages of the infection cycle.
1: J Biochem. 1980 Aug;88(2):525-32.
Process of attachment of phi X174 parental DNA to the host cell membrane.
Azuma J, Morita J, Komano T.
The phi X174-DNA membrane complex was isolated from Escherichia coli infected with phi
X174 am3 by isopycnic sucrose gradient centrifugation followed by zone electrophoresis. The
phi X174 DNA-membrane complex banded at two positions, intermediate density membrane
fraction and cytoplasmic membrane fraction, having bouyant densities of 1.195 and 1.150 g/ml,
respectively. Immediately after infection with phi X147, replicating DNA was pulse-labeled and
then the incorporated label was chased. The radioactivity initially recovered in the intermediate
density membrane fraction migrated to the cytoplasmic membrane fraction. The DNAs from
both complexes sedimented mainly at the position of parental replicative form I (RFI). The phi
X174 DNA-membrane complex contained a speficic membrane-bound protein having a
molecular weigth of 80,000 which is accumulated in the host DNA-membrane complex. These
results suggest that when phi X174 DNA penetrated into cells in the early phase of infection,
single-stranded circular DNA was converted to parental RFI at a wall/membrane adhesion region
and migrated to the cytoplasmic membrane fraction, where the parental RF could serve as a
template in the replication of progeny RF.
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