View source for 1k91

[[Image:1k91.jpg|left|200px]]

 {{Structure
|PDB= 1k91 |SIZE=350|CAPTION= <scene name='initialview01'>1k91</scene>
|SITE= 
|LIGAND= 
|ACTIVITY= 
|GENE= 
|DOMAIN=
|RELATEDENTRY=[[1hhn|1HHN]], [[1k9c|1K9C]]
|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1k91 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1k91 OCA], [http://www.ebi.ac.uk/pdbsum/1k91 PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1k91 RCSB]</span>
}}

'''Solution Structure of Calreticulin P-domain subdomain (residues 221-256)'''


==Overview==
Calreticulin (CRT) is an abundant, soluble molecular chaperone of the endoplasmic reticulum. Similar to its membrane-bound homolog calnexin (CNX), it is a lectin that promotes the folding of proteins carrying N-linked glycans. Both proteins cooperate with an associated co-chaperone, the thiol-disulfide oxidoreductase ERp57. This enzyme catalyzes the formation of disulfide bonds in CNX and CRT-bound glycoprotein substrates. Previously, we solved the NMR structure of the central proline-rich P-domain of CRT comprising residues 189-288. This structure shows an extended hairpin topology, with three short anti-parallel beta-sheets, three small hydrophobic clusters, and one helical turn at the tip of the hairpin. We further demonstrated that the residues 225-251 at the tip of the CRT P-domain are involved in direct contacts with ERp57. Here, we show that the CRT P-domain fragment CRT(221-256) constitutes an autonomous folding unit, and has a structure highly similar to that of the corresponding region in CRT(189-288). Of the 36 residues present in CRT(221-256), 32 form a well-structured core, making this fragment one of the smallest known natural sequences to form a stable non-helical fold in the absence of disulfide bonds or tightly bound metal ions. CRT(221-256) comprises all the residues of the intact P-domain that were shown to interact with ERp57. Isothermal titration microcalorimetry (ITC) now showed affinity of this fragment for ERp57 similar to that of the intact P-domain, demonstrating that CRT(221-256) may be used as a low molecular mass mimic of CRT for further investigations of the interaction with ERp57. We also solved the NMR structure of the 73-residue fragment CRT(189-261), in which the tip of the hairpin and the first beta-sheet are well structured, but the residues 189-213 are disordered, presumably due to lack of stabilizing interactions across the hairpin.

==About this Structure==
1K91 is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1K91 OCA]. 

==Reference==
NMR structures of 36 and 73-residue fragments of the calreticulin P-domain., Ellgaard L, Bettendorff P, Braun D, Herrmann T, Fiorito F, Jelesarov I, Guntert P, Helenius A, Wuthrich K, J Mol Biol. 2002 Sep 27;322(4):773-84. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/12270713 12270713]
[[Category: Rattus norvegicus]]
[[Category: Single protein]]
[[Category: Bettendorff, P.]]
[[Category: Braun, D.]]
[[Category: Ellgaard, L.]]
[[Category: Fiorito, F.]]
[[Category: Guntert, P.]]
[[Category: Helenius, A.]]
[[Category: Herrmann, T.]]
[[Category: Wuthrich, K.]]
[[Category: hairpin]]

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