|
Figure 6.
Figure 6. Cryo-EM Densities for Residues 72-96 in the
Averaged µ1 Cryo-EM Map
(A) Close-up stereo view of a
region near the base of two adjacent µ1 trimers, looking toward
the virion interior. Cryo-EM densities (gray net, contoured at
2.0 s) are fitted with the X-ray crystal models of two µ1
trimers (light-blue and brown ribbon traces, respectively).
Extra cryo-EM densities forming a U-shaped loop (green net) were
assigned to residues 72-96. Black and blue spheres, abutting the
two ends of the U-shaped densities, identify the positions of
residues Ile71 and Asp97, respectively, in the light-blue
subunit. A short a helix (residues 122-127), colored purple in
the otherwise brown subunit, is slightly displaced from the
attributed cryo-EM densities, apparently owing to contacts with
the 72-96 loop.
(B) Same as shown in (A), but with a
tentative ribbon trace (magenta), including an a helix, built
into the extra cryo-EM densities ascribed to residues 72-96.
(C) Same as shown in (B), but viewed in an orthogonal
direction, from the left side of (B) to illustrate apparent
interactions between the 72-96 (magenta) and the 51-62 (cyan)
loops. The 51-62 loop is clearly displaced from the associated
cryo-EM densities. A b strand formed by residues 63-65 (black)
also contacts the 72-96 loop. The 10 Å scale bar also applies to
(A) and (B).
(D) Bottom view (from virion interior) of two
adjacent µ1 trimers (light-blue and brown) in the atomic model.
Putative traces for the two 72-96 loops at the trimer-trimer
interface are shown in magenta. The scale bar is 25 Å.
|
