A potent vasoconstricor peptide produced by mammalian vascular endothelial cells. The structure has an alpha-helix segment and two disulfide bonds. The N-terminal and C-terminal ends of the peptide may be identified, and hydrophobic and polar regions shown. For clarity, hydrogen atoms are not displayed.
A single peptide secreted by tumor cells. It is a potent inhibitor of neovascularization. It specifically binds to endothelial cells and induces their proliferation. Three alpha-helices and two sets of three antiparallel beta-sheets are evident components of the tertiary structure. Hydrogens are not displayed.
The extracellular fibrous protein collagen is a major component of connective tissues such as skin, tendons and cartilage. Two unique amino acids, hydroxyproline (Hyp) and hydroxylysine (Hyl), are present in significant amounts. The hydroxylysine units are often glycosylated. Collagen contains more Gly (33%) and proline derivatives (20 to 24%) than do other proteins. There is very little Cys or Trp present. The primary structure of collagen has a frequent repetitive pattern, Gly-Pro-Hyp (or Lys or Hyl). Collagen chains are approximately 1000 units long, and assume an extended left-handed helical conformation (the influence of proline rings). Three such chains wind about each other with a right-handed twist to generate a rope-like superhelical quaternary structure, stabilized by interchain hydrogen bonding. The model shown here is a synthetic collagen made up of repeating -Gly-Pro-Pro- segments. The "color chain" button designates the separate chains. The initial view of this structure from the end shows its symmetry.