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Figure 5.
Figure 5. The MORE- and PORE-Type Interfaces Are
Structurally Conserved in the POU Transcription Factor Family(A)
Sequence alignment of POU domains from different transcription
factors reported to dimerize in a DNA sequence-dependent
fashion. Amino acid residues conserved to Oct-1 are indicated by
dots. Residues involved in POU[S]-POU[H] interface formation in
the Oct-1/MORE and Oct-1/PORE crystal structures are highlighted
red and blue, respectively. Serine and threonine residues that
are candidates for posttranslational modification are marked in
yellow.(B and C) Oct-4/MORE and Oct-4/PORE homology model built
with WHAT IF (Vriend, 1990) using the coordinate file of the
respective crystal structures with Oct-1. Due to sequence
variation in the two interfaces, both models predict new side
chain-specific H bond formations between the two POU molecules.
This finding demonstrates the versatile nature of the MORE- and
the PORE-type interface. Ser159 and Ser107 play a central role
in the MORE- and PORE-like interaction, respectively.(D) EMSA
using an Oct-4 mutant containing a phosphorylation imitating
mutation in the MORE dimerization interface (S159E). The
Ser159Glu mutation selectively disrupts dimerization only on the
MORE but not on the PORE motif. WT, wild-type Oct-4 protein;
Igκ, oligonucleotide containing the octamer motif from the
immunoglobulin kappa chain promoter; M, monomer; and D, dimer
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