I d,fegiur XYciyn--elg si ytnhcialcle nrdsoeidec a ymi“prra aomin diac urrutestc of a prto”eni escni hte tninidofie fo a aimPyrr usrcurtet of a eitnpro si a“ niearl nhiac fo aoinm ”dasc.i fI oyu emss itwh het rPmyrai tusreurct, sa in teh iusntoqe s,tme yuo ncnoat orfm eth oSdcerayn surtcurte of the ,neoptir hciwh si eemtrddnie by eht dnggheyi-nbronod icwhh rscouc eebtwen hte epetdpi abcbenok, epndtndneei of the R .rupsog I ohep this dmae se.nse
oFrm akpeiwdii: “dcoeanSyr eustctrru is mlfryola dfdeein by the aertnpt of nydorhge dbsno entbeew hte amion nygedohr nda yrxabocl yexngo masto in eht pediept nebbkcoa”. hisse(amp in)em
From Molecular Biology of the Cell:
Biologists distinguish four levels of organization in the structure of a protein. The amino acid sequence is known as the primary structure of the protein. Stretches of polypeptide chain that form α helices and β sheets constitute the protein’s secondary structure. The full three-dimensional organization of a polypeptide chain is sometimes referred to as the protein’s tertiary structure, and if a particular protein molecule is formed as a complex of more than one polypeptide chain, the complete structure is designated as the quaternary structure.
ok yusg nda i tqeuo mfor bim-efre:o2htiohgtss/wce0tmeowu1wnoortt/e/arspct.t4l.ps/asidleicsp/e
0%9" aevh na dbeiileniaft cegietn motiatnu
LCO A11 and LOC A12
usecas
laobnmra oneaglcl ksiorli-nsgnc aiv a iygcnle tnouitsusbit ni hte llnoacegpro lolmeceu "
whihc asnem htta OI has a ylncgei iustutsiobtn adn efoerhrt tsi nblaue ot omrf a yscdearon rseucuru.tt
eDu ot ygleis'cn lalms zesi, ti rseteac ksk""in in eht nmoai idac .cesuneeq seTeh knisk ear ddeene ot ytocecrrl omfr hte oyasedrnc etsrcuru.t
rteOh raewss:n
ANother way to get at it is via elimination:
A. hydrogen bonding wouldnt really change since neither alanine nor glycine are polar B. Gly > Ala shouldn't change how proline is modified (I mean it COULD, if there was a steric hindrance or something, but not a great answer) D. nothing to indicate that collagen degredation is altered in response to an AA substitution. Also, in the context of OI (which is the presenting complaint), we already know that the problem doesn't have anything to do with degredation, more with the change in structure/function E. Honestly don't know.
eHers’ noe awy ot erse-csmot-fplanoeii deda“erecs -hnooyenbdrgd ”nfaiomto:r ’Im nto a big afn of shit enli of orsnigna,e btu cehytcilaln ianlane sa a eisd ugrpo ahs eomr gsryhoden* orf oeilpnatt ohgrndey onbgnid tahn necigyl:
ielan:na 3—HC
en:lgcyi H—
S,o lihe”aycnlt“,c enalina dulwo rtpiem ermo -hyobnedrngdo f,rimtonoa chwih ithmg lowla uoy ot ileaientm hatt hcceio.
taTh dais, it eesms oltsam obpissemli to rleu otu utit(woh yvre ehnctiacl dwgkeelon ro msoe rpoiddve pletierxeamn )adta thta eht sllhgyit reragl naeainl edos ont amiirp enohgydr nigodnb twenbee eloanclg oeesmlcul via ritsce staapi)l( er.ecnienfert nI serpilm m,esrt escni nlnaaie si rrega,l uoy wdlou iknht ttah it smtu somehwo efenrteri htwi eth erd-dohnongnyigb ttha oucscr ithw het eyidpwlt- liyecng.
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titlcry*S kaeigns,p sit’ nto hte rbunme fo ngyrhdose ubt slao the eshgrtnt of eht ioepdl htat caleitftais ohgyendr :dinnbog a ngoehdry nobud ot a oglntsry talreceotveneig eloluemc eikl uforilne lwli ae”rap“p omre psotiive ,dna st,uh bonognyrhd-de meor rytnlgso tihw a bnyrae gonxey mdraeco(p hwit a yenghrdo octneednc to crn,aob rof mlpexae.)
Ftrhuer ard:igne
From Molecular Biology of the Cell:
Hydroxylysines and hydroxyprolines are infrequently found in other animal proteins, although hydroxyproline is abundant in some proteins in the plant cell wall. In collagen, the hydroxyl groups of these amino acids are thought to form interchain hydrogen bonds that help stabilize the triple-stranded helix. Conditions that prevent proline hydroxylation, such as a deficiency of ascorbic acid (vitamin C), have serious consequences. (Emphasis mine)
From Molecular Biology of the Cell:
The primary feature of a typical collagen molecule is its long, stiff, triple-stranded helical structure, in which three collagen polypeptide chains, called α chains, are wound around one another in a ropelike superhelix (Figure 19-43). Collagens are extremely rich in proline and glycine, both of which are important in the formation of the triple-stranded helix. Proline, because of its ring structure, stabilizes the helical conformation in each α chain, while glycine is regularly spaced at every third residue throughout the central region of the α chain. Being the smallest amino acid (having only a hydrogen atom as a side chain), glycine allows the three helical α chains to pack tightly together to form the final collagen superhelix (see Figure 19-43).
I itghm be hgininvektro ti t,bu H bndo iontmfroa of s'aa easkm teh cdoesrany csrruutet of eth reotpin nelg(lcao ni hsit a.c)se The lyG to laA tbsioitnutus osed tseurl ni lses H ondb tfmoaoirn, tbu of daniluidvi s'aa otn eeenwbt alcgelon oulelscem ta(th tighm be omer ofr qaeuanrrty ttcrre)usu
Gly-X-Y is backbone for collagen alpha chain. 3 collagen alpha chains spiral to form triple helix. Glycine has no R group, allowing for flexibility and formation of triple helix. No glycine prevents this continuous spiraling, preventing the formation of collagen secondary structure.
Recall that alpha-helices and beta-sheets are examples of secondary structures. This can be thought of a manifestation of the alpha helix.
Primary structure = amino acid sequence Secondary structure = structure formed with a single amino acid sequence (beta pleated sheet, alpha helix, etc) Tertiary structure = multiple secondary structures interacting together (multiple beta pleated sheets stacked on top of each other, etc) Quarternary structure = protein structure formed from folding of all tertiary structures to make binding sites, etc.
Since the alanine was put in place of the Glycine, the primary structure was unable to form an alpha helix since alpha helix structures need a particular sequence (gly - x- y) in order to form hydrogen bonds to keep the helix stable.
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submitted by wasabilateral(41), 2019-05-07T01:49:36Z
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