Question

Abnormalities in the synthesis or structure of collagen cause dysfunctions in cardiac organs, bone, skin, joints, and cyes. Problems may result from abnormal collagen genes, abnormal posttranslational modifications of collagen, or deficiency of cofactors needed by enzymes responsible for posttranslational modifications. Scurvy, a lack of vitamin \(\mathrm{C},\) is an example of the last type. In collagen: A. intrachain hydrogen bonding stabilizes the native structure. B. three chains with polyproline type helical conformation can wind about one another to form a superhelix because of the structure of glycine. C. the \(\varphi\) angles contributed by proline are free to rotate. D. regions of superhelicity comprise the entire structure except for the \(N\) - and \(C\) -termini. E. crosslinks berween triple helices form after lysine is converted to allysine.

Short answer

Based on the given information, indicate whether each statement about the collagen is true or false: A. Intrachain hydrogen bonding stabilizes the native structure. - True B. Three chains with polyproline type helical conformation can wind about one another to form a superhelix because of the structure of glycine. - True C. The \(\varphi\) angles contributed by proline are free to rotate. - False D. Regions of superhelicity comprise the entire structure except for the \(N\) - and \(C\) -termini. - True E. Crosslinks between triple helices form after lysine is converted to allysine. - True

Step-by-step solution

Statement A

Intrachain hydrogen bonding stabilizes the native structure. *True*. In collagen, hydrogen bonding takes place between carbonyl and amide groups within a single chain, which helps stabilize its triple-helical native structure.

Statement B

Three chains with polyproline type helical conformation can wind about one another to form a superhelix because of the structure of glycine. *True*. Collagen is composed of three polypeptide chains, each having a polyproline type (PP II) helical conformation. Every third residue in the chains is glycine, which allows the chains to come close to each other and form a superhelix, also known as the collagen triple helix.

Statement C

The \(\varphi\) angles contributed by proline are free to rotate. *False*. In collagen, proline contributes to the formation of the left-handed polyproline type (PP II) helix structure. Proline is characterized by a cyclic structure that limits its \(\varphi\) (phi) angle rotation, which stabilizes the helix.

Statement D

Regions of superhelicity comprise the entire structure except for the \(N\) - and \(C\) -termini. *True*. The collagen triple helix is formed by supercoiling of the three polyproline type helices. The regions of superhelicity cover most of the structure, but the amino (N-) and carboxyl (C-) termini are not part of the triple helical regions.

Statement E

Crosslinks between triple helices form after lysine is converted to allysine. *True*. In collagen, intermolecular crosslinks between the triple helices are required for the formation of stable and functional fibers. These crosslinks form when specific lysine residues are enzymatically converted to allysine, allowing covalent bonding between adjacent collagen triple helices.