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Figure 2.
Figure 2. Crystal Structure of the PduU Shell Protein
(A
and B) (A) The PduU hexamer viewed along the sixfold axis and
(B) perpendicular to the sixfold axis with distinct protein
chains colored separately. The outline drawn around the hexamer
(A) illustrates its presumed packing in the microcompartment
shell among the other (more abundant) homologous shell protein
hexamers (e.g., PduA, PduB, PduB′, and PduJ). A prominent
feature of the PduU hexamer is the six-stranded, parallel
β-barrel formed by one N-terminal β strand from each monomer.
Whether this feature at the top of the hexamer faces out toward
the cytosol or toward the interior of the microcompartment has
not been established.
(C) Ribbon diagram depicting the PduU
monomer, colored from blue (N terminal) to red (C terminal).
Over residue positions 19–109, the chain adopts a variation of
the typical bacterial microcompartment (BMC) fold (Kerfeld et
al., 2005). The 18 amino-terminal and eight carboxy-terminal
residues form novel secondary structural elements.
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