Biology Reference
In-Depth Information
To gain insight into the structural basis of the inhibitory activity of
compstatin, we have employed a combination of NMR-based strategies,
positional scanning, site-directed mutagenesis, and computational
modeling approaches [35,36]. This multidisciplinary approach resulted
in the resolution of the structure of compstatin and helped us elucidate
several structure/function aspects of its activity. NMR studies of comp-
statin's structure revealed a molecular surface that comprises a polar
patch and a nonpolar region. The polar part (residues 5-11) includes a
type I b-turn and the nonpolar part (residues 1-4 and 12-13) includes
the disulfide bridge that cyclizes the peptide.
Compstatin was subsequently subjected to several rounds of
sequence and structure optimization using a comprehensive and
integrative strategy comprising biophysical, molecular, and computa-
tional methods [25, 37-42]. The structure/activity relations determined
in this structure-based rational design opened the way for a second
round of phage-displayed random peptide library design, which
produced a peptide that was 4-fold more active than the parent
peptide [40].
Extending on our experimental high-throughput screening strategy,
we decided to use compstatin as a model peptide for in silico combina-
torial design, using a novel two-step computational optimization
methodology. This round of design yielded a 16-fold more active
analog than the parent peptide with sequence Ac-I[CVYQDW-
GAHRC]T-NH 2 [43-46].
In an effort to integrate the data derived from our structure/func-
tion studies of compstatin into a new generation of C3-inhibitory
peptides, we have recently produced new compstatin analogs, some
of which were also expressed in E. coli using an intein-mediated expres-
sion system [47,48]. This approach has yielded an analog that is about
220 times more active than the original compstatin [48]. Finally, a
different round of in silico studies was performed using molecular
dynamics simulations, in our effort to understand the dynamic charac-
ter of compstatin [49]. Collectively, these studies underscore the concept
that bioactive peptides should be regarded as dynamic and flexible
molecules rather than rigid structures when studying their binding
properties. This concept is integral to our research for more effective
complement inhibitors and should be taken into consideration in any
drug design effort that involves peptide screening, synthesis, and
structure manipulation.
Studies on the C5a/C5aR Interaction Using Synthetic C5aR
Antagonists
Considerable effort has been devoted to characterizing the interaction
of the complement anaphylatoxin C5a with its receptor C5aR, in sev-
eral biological contexts. In this direction, an array of synthetic and
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