||Fred W. Keeley
Ph.D., University of Manitoba, 1970
|Hospital for Sick
Children, McMaster Building, Room 7003
Synthesis and Assembly of Elastin
and Elastin-Like Structural Proteins of the Extracellular Matrix
Elastin is the major structural protein
of the large blood vessels, giving these tissues the physical properties
of extensibility and elastic recoil which are essential for their
physiological function. Our laboratory has had a long-standing interest
in the biochemistry of elastin, it's synthesis and assembly in the
extracellular matrix, its role in cardiovascular development and
diseases such as atherosclerosis and hypertension and its functional
and evolutionary relationship to other glycine-rich, elastin-like
structural proteins in a variety of tissues and species.
Sequence, Structure, and Self-Assembly of Elastin
To achieve the exceptional durability,
structural integrity and elastomeric properties of the elastic matrix,
monomers of elastin must be aligned into the appropriate architecture
in the extracellular space and then covalently crosslinked into
an extended polymer. How this ordered assembly of elastin monomers
takes place is not well-understood. We have demonstrated that interactions
between hydrophobic domains in the elastin monomers themselves play
a role in their alignment and in the assembly of elastin polymers.
We are particularly interested in understanding the relationship
between the sequence and structure of elastin and it's functional
properties, including both its ability to undergo this crucial first
step of self-assembly and the mechanical properties of the final
polymeric matrix formed from the protein.
We are characterizing the self-assembly
properties of recombinant polypeptides based on the sequence and
domain structure of elastins and have shown not only that these
simplified polypeptides can mimic the ability of elastin monomers
to organize themselves into polymers through hydrophobic self-assembly
, but also that these polymers can be stabilized by crosslinking
into biomaterials with physical properties remarkably similar to
those of the native polymeric elastin.
Phylogenetic Variations in Elastin Sequence, Structure and
A second approach to understanding
sequence-structure-function relationships in elastin has involved
an analysis of variations in sequence of both hydrophobic and crosslinking
domains over a broad phylogenetic range. We have now extended the
phylogenetic range of known elastin sequences to include teleost
and more amphibian elastins. The results of these studies have also
provided important new insights into the evolutionary history of
elastin and suggested not only design features of the protein which
are conserved across this broad range of species and are therefore
likely important for it's fundamental properties of extension and
recoil, but also sequence variants which may be determinants of
variations in physical properties of elastic tissues between species.
Evolution of Elastin: Relationships to Other Glycine-Rich
Matrix Proteins of Lower Vertebrates and Invertebrates.
The evolutionary origins of elastin
are obscure. While elastin is a major component of large arteries
in virtually all species above agnathans, the protein is absent
from arterial tissues of agnathans such as lamprey and hagfish,
as well as from invertebrates with a closed circulatory system.
We and our colleagues have shown, however, that elastin-like proteins
form the major structural element of cartilaginous tissues in these
lower vertebrates and invertebrates. We are characterizing the family
of elastin-like proteins in lower vertebrate and invertebrate cartilage.
To date we have cloned, sequenced and characterized a major elastin-like
structural protein of lamprey skeletal cartilage, and are presently
in the process of detailed characterization of several other members
of this family of cartilage proteins.
electron micrograph of the surface of a biomaterial made from elastin
made from elastin polypeptides mounted for determination of elastic
properties of biomaterials made from elastin polypeptides: stress/strain
curves for repeated cycles of loading and unloading
S. Vieth, C. M. Bellingham, F. W. Keeley, S. M. Hodge, and D. Rousseau,
Microstructural and Tensile Properties of Elastin-based Polypeptides
Crosslinked with Genipin and Pyrroloquinoline Quinone, Biopolymers 85,
J. T. Cirulis, C. M. Bellingham, E. C. Davis, D. Hubmacher, D. Reinhard, R.
P. Mecham and F. W. Keeley, Fibrillins, Fibulins and MAGP Modulate the
Kinetics and Morphology of In Vitro Self-Assembly of a Recombinant
Elastin-like Polypeptide, Biochemistry 47, 12601-12613, 2008.
M. Miao, R.J. Stahl, W. Reintsch, E. Davis and F. W. Keeley,
Characterization of an Unusual Tropoelastin with Truncated C-Terminus in
the Frog, Matrix Biology 28, 432-441, 2009.
L. D. Muiznieks, A. S. Weiss and F. W. Keeley.Strucutral Disorder and
Dynamics of Elastin, Canadian Journal of Biochemistry and Cell Biology,
Biochem. Cell Biol. 88, 239-250, 2010.
J. T. Cirulis and F. W. Keeley, Kinetics and Morphology of Self-assembly of
an Elastin-like Polypeptide Based on the Alternating Domain Arrangement of
Human Tropoelastin, Biochemistry 49, 5726-5733, 2010
L. D. Muiznieks and F. W. Keeley, Proline Periodicity Modulates the
Self-Assembly Properties of Elastin-Like Polypeptides, J Biol Chem 285: