Immediate research seems to point generally towards proline and hydroxyproline.
Quote
Collagen (kŏl′əjən), any of a group of proteins found in skin, ligaments, tendons, bone and cartilage, and other connective tissue. Cells called fibroblasts form the various fibers in connective tissue in the body. The fibroblasts produce three types of fibers to form the ground substance: collagen, elatin, and the reticulum. Collagen consists of groups of white inelastic fibers with great tensile strength. These fibers include fine fibrils, which are composed of even finer filaments, visible only through the electron microscope. Collagen protein contains an unusually high percentage of the amino acids proline and hydroxyproline. X-ray diffraction studies provide evidence that the protein forms a wavy band, a coiled chain with periodic, i.e., repeating, arrangement of its amino acids… (Just something I find funny: )
…A group of diseases including…lupus… (It’s always lupus!!)
MLA Citation:
“Collagen.” Columbia Electronic Encyclopedia, 6th Edition 1 (2009): 1. MAS Ultra - School Edition. EBSCO. Web. 26 Oct. 2009.
AMA Citation:
Collagen. Columbia Electronic Encyclopedia, 6th Edition [serial online]. January 2009;( 1):1. Available from: MAS Ultra - School Edition, Ipswich, MA. Accessed October 26, 2009.
Edit: And now to pass out and get up in two hours for college classes.