To see the cavity:

Display the Tetramer in Beta FirstGlance in Jmol.
Click on "Jmol" (lower right below molecule), then click Console.
Copy the script below, paste it into the bottom box of Jmol's console, and press Enter.

slab off
spin off
isosurface delete
restrict none
refresh
reset
select :a and ligand
center selected
rotate z 104.77
rotate y 47.49
rotate z 50.6
zoom 440
restrict :a
rotationRadius = 84.39
spacefill
color atoms chain
color atoms translucent -1
select :a and ligand
spacefill off
wireframe 0.5
color atoms opaque
color cpk
select :a and gln136
color atoms opaque
select :a
isosurface minset 250 POCKET cavity 1.2 5
console off