Identification and characterization of receptors for riboflavin carrier protein in the chicken oocyte - Role of the phosphopeptide in mediating receptor interaction

Sooryanarayana, * and Sarkar, Shubhashish and Adiga, Radhakantha P and Visweswariah, Sandhya S (1998) Identification and characterization of receptors for riboflavin carrier protein in the chicken oocyte - Role of the phosphopeptide in mediating receptor interaction. In: Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1382 (02). pp. 230-242.

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Abstract

Riboflavin carrier protein (RCP) is a phosphoglycoprotein found in the egg and the serum of laying birds and other animals. We have investigated the binding of chicken RCP (cRCP) to membranes prepared from the whole chicken oocytes. RCP binding had an absolute requirement for calcium, with an affinity (K-d 10(-8) M) high enough to be physiologically relevant. Ligand blotting experiments using labeled RCP and vitellogenin, with proteins solubilized from oocyte membranes, indicated that RCP and vitellogenin bound specifically to three proteins of Mr 380, 260 and 110 kDa. Vitellogenin also bound to proteins of Mr 515 kDa and 97 kDa similar in size to those identified by receptor associated protein of RAP. Reduced and carboxyamidated RCP inhibited the binding of I-125-labeled RCP to chicken oocyte membranes, but recombinant RCP expressed E. coli coil, and dephosphorylated RCP, failed to interact with the receptors, indicating that post-translational modifications were necessary for ligand-receptor interaction. The purified phosphopeptide, prepared from tryptic digests of egg white RCP, was able to inhibit the binding of RCP to the receptor proteins, with an affinity comparable to native RCP indicating that the phosphopeptide sequence present in RCP sen es as the focal point for RCP-receptor interactions.

Item Type:	Journal Article
Publication:	Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	riboflavin carrier protein;chicken oocyte;vitellogenin;LDL receptor;LRP.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	12 Aug 2009 10:56
Last Modified:	01 Mar 2012 07:08
URI:	http://eprints.iisc.ac.in/id/eprint/18702

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