Appeal No. 2000-0630
Application No. 07/780,717
the minimal active core must be smaller, because the active streptavidin fusion protein
made by Sano lacks residues 13 and 14 (see Figure 1, part B).
We also disagree with the examiner’s statement that “[Sano] suggest[s] truncating
SA at both the N- and C-termini in order to solve any aggregation problems.” Sano actually
states that “the N-terminal region has been truncated in our streptavidin preparation by the
deletion of the corresponding coding region, [thus,] it is likely that the C-terminal region of
the mature streptavidin is responsible for the aggregation, although participation of the N-
terminal region cannot be excluded.” Page 146. In any case, Sano suggests that
“hydrophilic amino acid residues . . . might be responsible for the intermolecular
interactions” leading to aggregation. Id.
Hendrickson outlines two objectives: to examine the biophysical and
biotechnological properties of streptavidin in refined crystallographic detail, and to provide
a test of multiwavelength anomalous diffraction (MAD) methodology; the focus of the
reference is on methodology. Hendrickson describes the “elegantly simple $-barrel
structure” of the streptavidin protomer and also describes the assembly of the protomers
into the known tetramer, and pinpoints the location of biotin in the structure. Page 2193.
Hendrickson further explains (page 2194) that
"
The initial C trace included positions 14-136 from the possible 13-139
sequence of the core streptavidin chain. Density for the terminal residues
was weak, and thus the initial fitting for the molecule was restricted to
residues 14-133. Only residues 16-133 are included in our most recent
model. These suffice to complete the $-barrel and leave the cleaved termini
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