Jason F. Kreisberg, Scott D. Betts,
and Jonathan King (2000) Protein Science,
accepted.
ß-helix Core
Packing within the Triple - Stranded Oligomerization Domain of the
P22 Tailspike.
The P22 tailspike adhesin
contains a right-handed parallel ß-helix domain of 400
residues in 13 tightly packed coils. The ß-helix domains of
three identical subunits are bundled side-by-side in the trimer
and make predominantly hydrophilic subunit-subunit contacts
(Steinbacher et al., 1994, Science 265, 383-386). After the 13th
coil the three individual ß-helices terminate and the chains
wrap around each other to form three interdigitated ß-sheets
forming the walls of a triangular prism. The b-strands then
separate and form anti-parallel b-sheets, but still defining a
triangular prism in which each side is a ß-sheet from a
different subunit (R. Seckler, 1998, J. Struct. Biol. 122,
216-222). The subunit interfaces are buried in the triangular core
of the prism, which is densely packed with hydrophobic side chains
from the three ß-sheets. Examination of this structure
reveals that its packed core maintains the same pattern of
interior packing found in the left-handed ß-helix, a
single-chain structure. This packing is maintained in both the
interdigitated parallel region of the prism and the following
anti-parallel sheet section. This oligomerization motif for the
tailspike ß-helices presumably contributes to the very high
thermal and detergent stability which are a property of the native
tailspike adhesin.
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