Biology Reference
In-Depth Information
common multiple of two and three, that is, six. This does not, how-
ever, fully disprove the possibility of the functionality of a stoi-
chiometry of five, which has been the stoichiometry postulated in
other models.
111
In the model, the five vs. six discrepancy was inter-
preted as that one copy of the pRNA dissociates from initial hexam-
eric pRNAs after binding to procapsids, leaving five pRNAs still
bound.
111
The pentameric theory is based on the fact that pRNA
binds to the procapsid containing a pentameric vertex. However,
recent publications have revealed that the foothold for the pRNA is
the connector, not the procapsid protein.
149
Further scrutiny to argue
against a stoichiometry of five involved in the DNA translocation
process was accomplished by testing two sets of pRNAs. The first set
was termed “Four Plus One” and the second was “Six Minus One.”
Both sets were found to be inactive in DNA packaging (manuscript
in preparation).
“Four Plus One”
A key finding in pRNA research was that the mixing of two inactive
pRNAs with complementary interlocking left and right loops restores
DNA-packaging activity. For example, mixing two inactive pRNAs
with
X-y´
and
Y-x´
resulted in production of infectious virions, which
suggested that the right-hand loop
X
of pRNA
X-y´
can pair with the
left-hand loop
x
´ of pRNA
Y-x
´. Incorporation of one active
monomer into the “Two Dimer Set” containing self-complementary
loops can compose the “Four Plus One” set. For instance, mixing two
pRNAs
A-a
´ with monomer pRNA
Y-x
´ can make up a five-member
pRNA ring by trans-complementary interlocking. In this case, the Y
and
x
´ are the two loops that were complementary to the
a
´ and
A
,
respectively. Since monomer pRNA
Y-a
´ shows significant DNA-
packaging activity, right-hand loop
Y
can pair with left-hand loop
a
´.
However, this combination for the formation of a five-pRNA ring
(two plus two plus one) blocks the DNA packaging, indicating that
the five-member pRNA ring formed by “Four Plus One” is inactive
(Table 8).
