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Figure 1.
Figure 1. The Bacteriophage T4 DNA Packaging Machine
(A)
The T4 procapsid during DNA packaging.
(B) The packaging
motor consists of the dodecameric portal protein gp20 and the
large terminase gp17. The gp17 molecule has an N-terminal domain
(gp17 N), which hydrolyzes ATP, and a C-terminal domain (gp17
C), which has nuclease activity and a DNA translocation
function.
(C) A stereo ribbon diagram of the RB49 gp17
C-terminal domain crystal structure with α helices colored in
cyan, β sheets silver, and loops brown. The termini are labeled
as N and C, and selected amino acids are numbered. A flexible
loop L2, shown as a dotted line, was not seen in the electron
density. A magnesium ion was detected in the electron density
and is shown as a purple sphere. Conserved acidic residues are
shown in ball-and-stick form.
(D) A stereo ribbon diagram
of the T4 gp17 crystal structure with α helices colored green
in the N-terminal subdomain I, yellow in the N-terminal
subdomain II, and cyan in the C-terminal domain. The β sheets
are colored silver, and loops are dark yellow. Selected amino
acids are numbered. Catalytic residues in the ATPase and
nuclease active centers are shown in ball-and-stick form, and a
bound phosphate ion is shown as cyan and red spheres.
The
ribbon diagrams were generated with the Chimera program
(Pettersen et al., 2004).
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