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Figure 5.
Gp16 intersubunit disulfide bonding of the stopper region and
DNA ejection. (A) Structure of the gp16 stopper. Residues
mutated to cysteine are identified by colors. (B and C) Effect
of stopper amino acid substitutions to cysteine in monomeric
gp16 (B; no cross-linking) and in its dodecameric assembled form
found in viral particles (C; formation of covalently bound
subunit dimers (upper bands) in oxidation conditions that were
efficiently reduced with 4 mM DTT). (D) DNA ejection from
virions bearing gp16 mutations was assayed by a DNase protection
method that reveals the amount of DNA not released from viral
particles (19). Ejection was triggered by receptor addition
using a ratio of 1,250 YueB780 dimers (19) per virion in the
presence and in the absence of 4 mM DTT. All results were
reproduced in at least 3 independent experiments.
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