Journal of Proteomics & Bioinformatics
Open Access

Abstract

Characterization of Rat Odorant Binding Protein Variants and its Post-Translational Modifications (PTMs): LC-MS/MS analyses of Protein Eluted from 2D-Polyacrylamide Gel Electrophoresis

Rajkumar R, Ilayaraja R, Alagendran S, Archunan G, Muralidharan A.R, Huang P. H, Ng WV and Chen-Chung Liao

Identification of odorant-binding protein (OBP) variants in mammalian system is of great importance to an understanding of their role in the binding of pheromones and other volatiles during chemical communication. Our previous proteomics studies have revealed the presence of OBP as well as confirming that, in the preputial gland of Indian commensal rat, the bound form of the protein associates with various farnesols. In addition to this, a recent mass spectrometry based proteomics analysis has shown that rat recombinant OBP undergoes post-translational modification (PTM) and there are a number of different variants in terms of phosphorylation. This suggests that the phosphorylation of OBP may affect its binding properties and the binding properties may change in the presence of phosphorylation. Thus, in the present investigation we have investigated these OBP variants. The variants were separated by 2DE-PAGE and protein identification was done using mass spectrometry. The results indicated that OBP has ten variants. Further, we employed anti serine phosphorylation immunoblotting in association with 2DE- PAGE to confirm that three spots were phosphorylation at a serine. In addition to immunoblotting, we also employed structural analysis, by multiple sequence alignment, secondary structural analysis, and a three dimensional analysis of the OBP’s using known lipocalin members. To the best of our knowledge, this is the first report demonstrating PTM variants of an OBP from the preputial gland of the Indian commensal rat.