PubMed:12270713 JSONTXT

{"project":"Lectin_function","denotations":[{"id":"T1","span":{"begin":53,"end":65},"obj":"GL_000284"},{"id":"T2","span":{"begin":53,"end":65},"obj":"GL_000285"},{"id":"T3","span":{"begin":53,"end":65},"obj":"GL_000286"},{"id":"T4","span":{"begin":53,"end":65},"obj":"GL_000287"},{"id":"T5","span":{"begin":53,"end":65},"obj":"GL_000288"},{"id":"T6","span":{"begin":53,"end":65},"obj":"GL_002216"},{"id":"T7","span":{"begin":53,"end":65},"obj":"GL_000283"},{"id":"T8","span":{"begin":53,"end":65},"obj":"GL_000262"},{"id":"T9","span":{"begin":53,"end":65},"obj":"GL_000263"},{"id":"T10","span":{"begin":53,"end":65},"obj":"GL_000264"},{"id":"T11","span":{"begin":53,"end":65},"obj":"GL_000265"},{"id":"T12","span":{"begin":53,"end":65},"obj":"GL_000266"},{"id":"T13","span":{"begin":53,"end":65},"obj":"GL_000267"},{"id":"T14","span":{"begin":53,"end":65},"obj":"GL_000268"},{"id":"T15","span":{"begin":53,"end":65},"obj":"GL_000269"},{"id":"T16","span":{"begin":53,"end":65},"obj":"GL_000270"},{"id":"T17","span":{"begin":53,"end":65},"obj":"GL_000271"},{"id":"T18","span":{"begin":53,"end":65},"obj":"GL_000272"},{"id":"T19","span":{"begin":53,"end":65},"obj":"GL_000273"},{"id":"T20","span":{"begin":53,"end":65},"obj":"GL_000274"},{"id":"T21","span":{"begin":53,"end":65},"obj":"GL_000275"},{"id":"T22","span":{"begin":53,"end":65},"obj":"GL_000276"},{"id":"T23","span":{"begin":53,"end":65},"obj":"GL_000277"},{"id":"T24","span":{"begin":53,"end":65},"obj":"GL_000278"},{"id":"T25","span":{"begin":53,"end":65},"obj":"GL_000279"},{"id":"T26","span":{"begin":53,"end":65},"obj":"GL_000280"},{"id":"T27","span":{"begin":53,"end":65},"obj":"GL_000281"},{"id":"T28","span":{"begin":53,"end":65},"obj":"GL_000282"},{"id":"T29","span":{"begin":76,"end":88},"obj":"GL_000284"},{"id":"T30","span":{"begin":76,"end":88},"obj":"GL_000285"},{"id":"T31","span":{"begin":76,"end":88},"obj":"GL_000286"},{"id":"T32","span":{"begin":76,"end":88},"obj":"GL_000287"},{"id":"T33","span":{"begin":76,"end":88},"obj":"GL_000288"},{"id":"T34","span":{"begin":76,"end":88},"obj":"GL_002216"},{"id":"T35","span":{"begin":76,"end":88},"obj":"GL_000283"},{"id":"T36","span":{"begin":76,"end":88},"obj":"GL_000262"},{"id":"T37","span":{"begin":76,"end":88},"obj":"GL_000263"},{"id":"T38","span":{"begin":76,"end":88},"obj":"GL_000264"},{"id":"T39","span":{"begin":76,"end":88},"obj":"GL_000265"},{"id":"T40","span":{"begin":76,"end":88},"obj":"GL_000266"},{"id":"T41","span":{"begin":76,"end":88},"obj":"GL_000267"},{"id":"T42","span":{"begin":76,"end":88},"obj":"GL_000268"},{"id":"T43","span":{"begin":76,"end":88},"obj":"GL_000269"},{"id":"T44","span":{"begin":76,"end":88},"obj":"GL_000270"},{"id":"T45","span":{"begin":76,"end":88},"obj":"GL_000271"},{"id":"T46","span":{"begin":76,"end":88},"obj":"GL_000272"},{"id":"T47","span":{"begin":76,"end":88},"obj":"GL_000273"},{"id":"T48","span":{"begin":76,"end":88},"obj":"GL_000274"},{"id":"T49","span":{"begin":76,"end":88},"obj":"GL_000275"},{"id":"T50","span":{"begin":76,"end":88},"obj":"GL_000276"},{"id":"T51","span":{"begin":76,"end":88},"obj":"GL_000277"},{"id":"T52","span":{"begin":76,"end":88},"obj":"GL_000278"},{"id":"T53","span":{"begin":76,"end":88},"obj":"GL_000279"},{"id":"T54","span":{"begin":76,"end":88},"obj":"GL_000280"},{"id":"T55","span":{"begin":76,"end":88},"obj":"GL_000281"},{"id":"T56","span":{"begin":76,"end":88},"obj":"GL_000282"},{"id":"T57","span":{"begin":90,"end":93},"obj":"GL_000284"},{"id":"T58","span":{"begin":207,"end":215},"obj":"GL_000248"},{"id":"T59","span":{"begin":207,"end":215},"obj":"GL_000249"},{"id":"T60","span":{"begin":207,"end":215},"obj":"GL_000250"},{"id":"T61","span":{"begin":207,"end":215},"obj":"GL_000251"},{"id":"T62","span":{"begin":207,"end":215},"obj":"GL_000252"},{"id":"T63","span":{"begin":207,"end":215},"obj":"GL_000253"},{"id":"T64","span":{"begin":217,"end":220},"obj":"GL_000248"},{"id":"T65","span":{"begin":231,"end":237},"obj":"GX_000027"},{"id":"T66","span":{"begin":231,"end":237},"obj":"GX_000045"},{"id":"T67","span":{"begin":460,"end":463},"obj":"GL_000248"},{"id":"T68","span":{"begin":468,"end":471},"obj":"GL_000284"},{"id":"T69","span":{"begin":583,"end":586},"obj":"GL_000284"},{"id":"T70","span":{"begin":861,"end":864},"obj":"GL_000284"},{"id":"T71","span":{"begin":941,"end":944},"obj":"GL_000284"},{"id":"T72","span":{"begin":963,"end":966},"obj":"GL_000284"},{"id":"T73","span":{"begin":1090,"end":1093},"obj":"GL_000284"},{"id":"T74","span":{"begin":1134,"end":1137},"obj":"GL_000284"},{"id":"T75","span":{"begin":1342,"end":1345},"obj":"GL_000284"},{"id":"T76","span":{"begin":1595,"end":1598},"obj":"GL_000284"},{"id":"T77","span":{"begin":1653,"end":1656},"obj":"GL_000284"},{"id":"T78","span":{"begin":1775,"end":1778},"obj":"GL_000284"}],"text":"NMR structures of 36 and 73-residue fragments of the calreticulin P-domain.\nCalreticulin (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."}