Figure 1.

Simplified scheme to show the origin of the determined crosslinks. Telopeptide Lys is converted to Hyl by TLH. The first step in crosslinking is the oxidation of telopeptide Lys or Hyl to aldehydes by lysyl oxidase. There are two pathways of formation of crosslinks, depending on whether the residue in the telopeptide is a Lys (allysine route) or a Hyl (hydroxyallysine route). The aldehydes react with specific Lys or Hyl residues in the triple helical domain on juxtaposed neighboring molecules to form difunctional intermediates that mature into trifunctional crosslinks. The two pathways lead to different types of crosslinks. Only the difunctional crosslinks that result from the hydroxyallysine route are able to mature into the trifunctional crosslinks HP and LP. Abbreviations: see legend of Fig. 3.