Fig 1.
The gp12 assembles into a ring-like decamer.
(A) Size exclusion chromatogram of the purified gp12 decamer. The peak corresponds to an estimated molecular weight of 471kDa, indicating a decamer (arrow). (B) Electron micrograph of the purified gp12 decamer negatively stained with uranyl acetate. Notice the dominant views are down the longitudinal axis of the gp12 decamer. Some side or tilted views are indicated with red arrows. (C) Electron micrograph of the frozen-hydrated gp12 decamer. Bar, 100 Å. (D) Class averages of the frozen-hydrated gp12 decamer. Enlarged views of two class averages are shown on the right. The 10-fold symmetry is clearly evident for both the crown (green arrowheads) and the stem domains (red arrows). The box size for class averages in the left panel is 309.8 Å.
Fig 2.
3D reconstruction of the gp12 decameric assembly.
(A) Class averages of the negatively stained gp12 decamer. The bottom row shows three class averages corresponding to stacked double decamers, demonstrating robustness of the 2D classification. The box size for class averages is 349.4 Å. (B) 3D reconstruction. Top left, front view. Top right, cutaway view. Bottom left, top view. Bottom right, tilted by 45° from the view on the left.
Fig 3.
Fitting of dsDNA into the channel of the gp12 decameric assembly.
The gp12 structure fitted with a standard dsDNA molecule (green molecular surface). (A), side view. (B), a view down the gp12 channel longitudinal axis. In (A), the front half of the gp12 assembly is computationally removed to show the channel width. Bar, 25 Å.
Fig 4.
Fitting the phiX174 H protein central domain X-ray structure (blue; RCSB PDB code 4JPP) into the stem domain of the Sf6 gp12 EM map (gold).
(A) The H protein structure is shown as ribbon diagram. The front halves of the H structure and the gp12 map were computationally removed for clarity. (B) A corss section of the gp12 map fitted with the H protein structure (molecular surface). (C) A view down the gp12 channel axis. The top half of the gp12 map was removed for clarity. The crown and stem domains of gp12 are indicated.
Fig 5.
Schematic representation of translocation of the DNA-injection proteins and the assembly of the DNA-injection device in the host envelope.
(A) The three DNA-injection proteins, gp12, gp11 and gp13, represented with an oval, triangle and trapezoid in blue, are packed in the phage particle. Note that the copy numbers of those proteins in the capsid and how they are arranged are not known. (B) upon attachment to the host cell, the DNA-injection proteins are translocated through the tail channel to the host cell envelope, where they assemble into an extended tube-like structure to allow delivery of phage DNA into the host cytoplasm. The arrangement of those proteins is not known and is drawn schematically. LPS, lipopolysaccharide; OM, outer membrane; PG, peptidoglycan; IM, inner membrane. The phage dsDNA is in green.