Sandbox GGC9
Crystal Structure of Collagen Adhesin and Collagen Complex
Collagen is one of the most abundance protein in the body. There are thought to be four types of collagen in which give rise to different structures of the body (bones, tendons, cartilage, skin, basement membranes, etc.) The collagenous domains have a characteristic triple helix structure where each of the participating polypeptides are repeating Gly-X-Y sequences that either form heterotrimeric or homotrimetric L-proline helices.[1] Both eukaryotic and prokayrotic express the collagen-binding protein such as ECM (Extracellular Matrix), celluar receptors, and bacterial adhesin. When there is a cleavage in collagen due to wounds, bacteria such as Staphylococcus aureus high affinity subsegment acts as apo-protein and binds to the collagen structure.
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Function
Collagen composed three α-chains (procollagen)in which synthesize in the ER. Collagen is a strong, rope-like molecule, that can forms stretch resistant fibers. These fibrils are the most abundant protein in our bodies. There are 20 different types of collagen in our bodies each can adapt to the needs of specific tissue. Collagen are multifunctional glycoproteins that play an important role in cellular morphogenesis, cell signaling, tissue repairing, and cell migration in the human body. These proteins are ubiquitously represent in tissues as part of the basement membrane (BM), in constitute a protective layer around the blood capillaries and are include in the extra cellular matrix (ECM). Which these tissues form protective and structural such as bones, tendons, ligaments, cartilage, and skin. The binding site for collagen types I and III is located in the VWF-A3 domain. However, bacterial rather have a slight different binding mechanism in which involves in cell wall anchored collagen adhesin (CNA).
Disease
Collagen-binding proteins(CBP) such as ECM (Extracellular Matrix) can be degrade via invasive pathogenic breach the basal lamina. Degradation of ECM can leads to major loss of mechanical containment molecules that protects the tissues from further pathogens. Furthermore, the pathogen will then degrade the interstitial space and connective tissues via ECM degrading proteases and/or the surface-bound plasminogen and matrix metalloprotein from the host. The adhesion of bacterial pathogen such as Staphylococcus aureus this particular adhesion calls "Collagen Hug", where CNA wraps around the collagen and further anchoring the bacteria .
Structural highlights
The collagen complex with binding protein represent in this view. Furthermore, this Ttriple helices represents the structure of procollagen (triple α-chain). The structural of hydroxyproline redisue of Hydroxylproline. Refering back to the the collagen-binding site of human Type I and Type III collagen, VWF-A3 is distinctly different from that of the homologous integrin α2 I domain, in which contains a hydrophilic binding site located at the top face of the domain.
This is the bacterial anchoring adhesin (CNA) of 2F6A collagen adhesin A,B,C,D or sometimes represent by N(s).
Based on the surface characteristics of the collagen-binding site, the proposal is that collagen-binding protein interact with collagen sequences containing positively charged and hydrophobic residues. The particular amino acid residuess in the binding protein in this case CNA interact with the residue of the collagen base on the polarity and non-polar molecules. Therefore, bacterial adhesion follows the same rule as eukaryotic binding factors. Bacteria CNA protein then wraps around the collagen active site and slightly tighten it with its CNA protein residue.
References
Molecular mechanics of Staphylococcus aureus adhesin, CNA, and the inhibition of bacterial adhesion by stretching collagen - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/Binding-mechanism-of-bacterial-adhesin-CNA-with-extracellular-matrix-protein-collagen_fig2_318074895 [accessed 23 Apr, 2018].
Zong Y, Xu Y, Liang X, Keene DR, Hook A, Gurusiddappa S, Hook M, Narayana SV. A 'Collagen Hug' model for Staphylococcus aureus CNA binding to collagen. EMBO J. 2005 Dec 21;24(24):4224-36. Epub 2005 Dec 15. PMID:16362049
