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Figure 1.
Structure of the E. coli ExoI/SSB-Ct complex. (A) Schematic
diagram of E. coli ExoI and SSB colored by structural features
[ExoI, Exonuclease domain (yellow), SH3-like domain (green), and
helical domain (red); SSB, oligonucleotide-binding (OB) domain
followed by ≈60 disordered C-terminal residues (orange)]. The
bar graph depicts evolutionary conservation of the SSB C
terminus (SSB-Ct) sequence among 284 bacterial SSB proteins as
percentage identity. (B) Ribbon diagram of ExoI bound to two
SSB-Ct peptides colored as in A. Mg^2+ ions are in magenta.
Dotted lines represent segments for which electron density was
not observed. (C) Surface representation depicting the binding
sites for two SSB-Ct peptides (A and B) bound to ExoI, colored
as in A. Selected ExoI residues are labeled. (D) Surface
representation as in C colored to model electropositive (blue)
and electronegative (red) potential. (E and F) Detailed views of
the peptide-A and peptide-B sites. The Arg-316 side chain from
apo ExoI (gray) is superimposed.
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