doi:10.1016/j.pep.2008.03.015
Copyright © 2008 Elsevier Inc. All rights reserved.
Expression in bacteria of small and specific protein domains of two transcription factor isoforms, purification and monospecific polyclonal antibodies generation, by a two-step affinity chromatography procedure
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Francisco Hernández-Torresa, José Rafael Pedrajasa, Amelia E. Aránega
, a,
and Francisco Navarro
, a, 
aDepartamento de Biología Experimental, Facultad de Ciencias Experimentales, Universidad de Jaén, Paraje de las Lagunillas, s/n, 23071 Jaén, Spain
Received 20 December 2007;
revised 10 March 2008.
Available online 28 March 2008.
Abstract
The detection and analysis of protein isoforms is a complicated task especially if they differ only in small specific domains. Obtaining specific polyclonal antibodies against these domains is a challenge, but if successful it can have a wide range of applications, such as in proteomics and immunochemical analysis. We show herein a method of overexpression and purification of two small specific domains corresponding to the isoforms b and c of the murine transcription factor Pitx2, and the generation and purification of monospecific polyclonal antibodies against them, by using a two-step affinity purification procedure, based on the use of CNBr–Sepharose matrix. Such a method also allows recovering monospecific polyclonal antibodies against the tag fusion peptide (C-LYTAG tag). The specificity of the isolated polyclonal antibodies was demonstrated by Western blot and immunohistochemical analysis. In addition, our protocol is easily scalable and allows the generation of monospecific polyclonal antibodies for large-scale analysis.
Keywords: Affinity purification; Isoform; Transcription factor; Polyclonal antibody; Protein epitope signature tags
Fig. 1. Schematic diagram of the regions cloned in pALEXB expression vector.
Fig. 2. C-LYTAG, C-LYTAG;E3PITX2B and C-LYTAG;E4PITX2C overexpression and purification. (A) Coomassie-stained SDS–PAGE of C-LYTAG;E3PITX2B overexpression after 4 h of salicylate induction. Thirty micrograms protein was loaded in each line. (B) Western blot analysis of gel in A by using the anti-C-LYTAG polyclonal antibody. (C) SDS–PAGE of purified C-LYTAG (1), C-LYTAG;E3PITX2B (2) and C-LYTAG;E4PITX2C (3) peptides (100 ng each). t0, no induction; t4, 4 h of salicylate induction.
Fig. 3. (A) Scheme of the two-step affinity chromatography procedure used for antibody purification based on CNBr–Sepharose matrix. (B) Commassie-stained SDS–PAGE of purified IgG. (1), (2) and (3) correspond to anti-C-LYTAG, anti-Pitx2b and anti-Pitx2c IgG, respectively.
Fig. 4. (A) Western blot analysis of 100 ng purified C-LYTAG (1), C-LYTAG;E3PITX2B (2), and C-LYTAG;E4PITX2C (3) recombinant proteins using affinity purified anti-C-LYTAG, anti-Pitx2b and anti-Pitx2c antibodies. (B) Western blot analysis of Pitx2b and Pitx2c in extracts of immortalized mice cardiomyocytes from E9.5, using the anti-Pitx2b and anti-Pitx2c antibodies. Thirty micrograms protein was loaded in each line. α-tubulin was used as a loading control. (C) Upper panel, nuclear immunolocalization of Pitx2b, Pitx2c and Nkx2.5 transcription factors, and Vimentin, in cultured cardiomyocytes. Lower panel, negative controls (including omission of the primary antibody).

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