Abstract
Abnormal levels of cross-linking in fibrillar collagen strands have been shown to cause a
number of human and animal diseases. Cross-linking is a vital step in fibrillogenesis and
contributes greatly to the structural integrity of collagenous tissues. Conversely, defects in
cross-link formation can significantly alter fibrillar organisation and lead to pathogenesis.
Because collagen cross-links form on collagen-specific hydroxylated lysine residues, an
understanding of the link between hydroxylysine and cross-link concentrations is needed
to determine whether the level of hydroxylysine, the stereochemistry of these
hydroxylysine residues, or other post-translational modifications such as glycosylation
affect the level of cross-linking in tissue. While some research has been done to elucidate
the connection between the two in different tissue types from the same animal, little has
been undertaken to relate hydroxylation and glycosylation of lysine and hydroxylysine to
the concentration and types of cross-links in different species. Furthermore, no research
has been done to compare the relative distribution of diastereomers of hydroxylysine even
within the same species. In order to make a valid comparison, collagen needs to be
purified from skin to a high degree and separated into different collagen types and sub-
structures as much as possible. To achieve this, the extraction and purification of collagen
from the skins of four different mammalian species displaying different skin tensile
strengths has been optimised. Different extraction methods were used to prevent the loss
of specific features of the collagens that were characterised that may otherwise be lost.
Amino acid analysis revealed that while the ratios of the two hydroxylysine diastereomers
differed between different animals and extraction methods, the differences were not
significant. Mass spectral analysis of cross-links showed that goat skin differed from the
other three animals in its cross-link profile. Amino acid analysis combined with mass
spectral analysis revealed that on average 70% of proline residues were hydroxylated, a
figure much higher than previously thought. Mass spectral analysis also revealed that there
are some differences between the glycosylation pattern of different animals, and the ratios
of the different types of collagen which are extracted from each animal. While these
findings need to be confirmed, they challenge some long held beliefs about the collagen
molecule and provide a firm foundation for future work.
Date
2019
Rights
The Author
Publisher
Massey University
Description
Table 2 and Figure 3 are re-used with the respective publisher's permission.
