De Novo Design of Proteins - Peptide and Protein Design for Biopharmaceutical Applications - page 227

without metal-ion complexation [114]. The folded peptide incorpo-
rated a type II 0 b-turn to assist in the formation of the b-hairpin

structure.
Baker and coworkers used their program, RosettaDesign, to design a
93-mer a/b protein, Top7, with a novel sequence and topology [51].
It was characterized by a range of biophysical techniques, which revealed
that it was monomeric and showed native-like behaviour. Structure
determination by X-ray crystallography revealed that it adopted the
intended fold. This important study thus combined computer design
using a program that is now generally accessible with full structural
characterization of the de novo protein.

6.4 PROTEINS ON TEMPLATES

This section describes steps toward a class of radically de novo -designed
proteins that are assembled on templates or scaffolds, which gives them
an artificial topology for the connection of secondary structural
elements (Figure 6.7). Mutter and coworkers suggested the term
'template-assembled synthetic proteins' (TASPs) to describe structures
in which peptide strands are anchored to regioselectively addressable
templates [115-117]. The secondary structural elements - so far mainly
a-helices have been used - are anchored to the template or scaffold to
preorganize them, typically in a parallel or antiparallel orientation.
Underlying this, there have been two basic but opposite assumptions:
either that the template to some extent controls or directs the distance

Figure 6.7 Schematic representation of the TASP concept, here depicted with four
helices (peptide sequences in Table 6.3)