Editing Hydroxyproline (section)

==== Non-collagen ====
Hydroxyproline is  found in few proteins other than collagen. For this reason, hydroxyproline content has been used as an indicator to determine [[collagen]] and/or [[gelatin]] amount. However, the mammalian proteins [[elastin]] and [[Argonaute|argonaute 2]] have collagen-like domains in which hydroxyproline is formed. Some snail poisons, [[conotoxin]]s, contain hydroxyproline, but lack collagen-like sequences.<ref name="gorres" />

Hydroxylation of proline has been shown to be involved in targeting [[Hypoxia-inducible factor]] (HIF) alpha subunit ([[HIF-1 alpha]]) for degradation by [[proteolysis]]. Under [[normoxia]] (normal oxygen conditions) [[EGLN1]][https://www.ncbi.nlm.nih.gov/gene/54583] protein hydroxylates the proline at the 564 position of HIF-1 alpha, which allows [[ubiquitylation]] by the [[von Hippel-Lindau tumor suppressor]] (pVHL) and subsequent targeting for [[proteasome]] degradation.<ref name="Jaakkola">{{cite journal | doi = 10.1126/science.1059796 | last1 = Jaakkola | first1 = P. | last2 = Mole | first2 = D.R. | last3 = Tian | first3 = Y.M. | last4 = Wilson | first4 = M.I. | last5 = Gielbert | first5 = J. | last6 = Gaskell | first6 = S.J. | last7 = Kriegsheim | first7 = A.V. | last8 = Hebestreit | first8 = H.F. | last9 = Mukherji | first9 = M. | last10 = Schofield | first10 = C. J. | last11 = Maxwell | first11 = P. H. | last12 = Pugh | first12 = C. W. | last13 = Ratcliffe | first13 = P. J. | year = 2001 | title = Targeting of HIF-alpha to the von Hippel-Lindau ubiquitylation complex by O2-regulated prolyl hydroxylation | journal = Science | volume = 292 | issue = 5516| pages = 468–72 | pmid = 11292861 | bibcode = 2001Sci...292..468J | s2cid = 20914281 | display-authors = 8 | doi-access = free }}</ref>