Defining substrate interactions with calreticulin: an isothermal titration calorimetric study

Gupta, Garima ; Gemma, Emiliano ; Oscarson, Stefan ; Surolia, Avadhesha (2008) Defining substrate interactions with calreticulin: an isothermal titration calorimetric study Glycoconjugate Journal, 25 (8). pp. 797-802. ISSN 0282-0080

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Official URL: http://www.springerlink.com/content/wu2q45656x31g4...

Related URL: http://dx.doi.org/10.1007/s10719-008-9151-7

Abstract

Calreticulin (CRT) is a soluble, lectin chaperone found in the endoplasmic reticulum of eukaryotes. It binds the N-glycosylated polypeptides via the glycan intermediate Glc1Man5-9GlcNAc2, present on the target glycoproteins. Earlier we have studied interactions of substrate with CRT by isothermal titration calorimetry (ITC) and molecular modeling, to establish that CRT recognizes the Glcα1-3 linkage and forms contacts with each saccharide moiety of the oligosaccharide Glcα1-3Manα1-2Manα1-2Man. We also delineated the amino acid residues in the sugar binding pocket of CRT that play a crucial role in sugar-CRT binding. Here, we have used mono-deoxy analogues of the trisaccharide unit Glcα1-3Manα1-2Man to determine the role of various hydroxyl groups of the sugar substrate in sugar-CRT interactions. Using the thermodynamic data obtained by ITC with these analogues we demonstrate that the 3-OH group of Glc1 plays an important role in sugar-CRT binding, whereas the 6-OH group does not. Also, the 4-OH, 6-OH of Man2 and 3-OH, 4-OH of Man3 in the trisaccharide are involved in binding, of which 6-OH of Man2 and 4-OH of Man3 have a more significant role to play. This study sheds light further on the interactions between the substrate sugar of glycoproteins and the lectin chaperone CRT.

Item Type:Article
Source:Copyright of this article belongs to Springer.
Keywords:Calreticulin; Isothermal Titration Calorimetry; Sugar-CRT Interaction
ID Code:56670
Deposited On:25 Aug 2011 10:26
Last Modified:25 Aug 2011 10:26

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