Chemistry Reference
In-Depth Information
Figure 5.6 Derivatization reagents for the preparation of
pyridoxamine conjugates of fatty acid binding proteins.
Figure 5.7 Single turnover, reductive amination, reactions promoted
by fatty acid binding protein-pyridoxamine conjugates.
5.3.3
Exploiting the Advantage of a Protein-based Scaffold
The next step in developing these protein-based catalysts was to take advantage of the
synthetic flexibility provided by a protein scaffold. Since the protein is encoded by a
DNA sequence, changes can be made in the gene that will result in modifications in
the protein. Mutagenesis and other genetic methods can produce alterations in the
protein framework much more rapidly than the organic synthesis required to
make changes in synthetic scaffolds. Initially, the position of catalyst attachment with-
in the cavity was varied to probe its effect on reaction rate and selectivity. For these
experiments, a different fatty acid binding protein (IFABP) was employed. The wild-
type IFABP contains no cysteine residues in its primary sequence and is, hence, a
useful template for the introduction of single cysteine residues at different positions
[46]. Cysteine residues were introduced at several positions, including V
60
,L
72
, and
A
104
, using site-directed mutagenesis. Figure 5.8 gives the locations of these mutations
within the protein structure.
