CBP Tag - Creative Diagnostics

Introduction to CBP tag

The calmodulin-binding peptide (CBP) tag was invented to purification of recombinant protein from bacteria based on high affinity for calmodulin with nanomolar affinity at physiological conditions in the presence of calcium. The CBP tag is derived from the C-terminal fragment of human muscle myosin light-chain kinase and thus is not recommended for purification of fusion proteins in eukaryotic cells because endogenous proteins can interfere with calmodulin in a calcium-dependent manner. The CBP-tag cannot be used for expression in eukaryotic systems, since many endogenous proteins in eukaryotes also interact with calmodulin.

Fig 1. Binding of calmodulin binding peptide (CBP) tagged hybrid protein to immobilized calmodulin in the presence of calcium ions.
(Source: Methods. Mol. Biol. 2000)

CBP tag for protein purification

Purification of fusion proteins based on a CBP tag was first described in 1992. The peptide consisted of 26 residues from the C-terminus of the soluble muscle myosin light chain kinase (MLCK).

A Ca2+-dependent calmodulin-binding peptide (CBP) tag is an attractive tag for affinity purification of recombinant proteins, especially membrane proteins, since elution is simply accomplished by removing/chelating Ca2+. Though calmodulin binds very strongly with CBP (nanomolar affinity), this interaction is dependent on calcium and the bound protein can be eluted in a single step using gentle buffers containing a calcium-chelating agent, such as EGTA. The CBP tag produced moderate purity protein from E. coli, yeast, and Drosophila extracts, but better purity from HeLa extracts.

Another application of the CBP-tag is for 32P isotopic labeling of the fusion protein, since the tag includes a protein kinase A target sequence.

Advantages of CBP tag

The 4-kDa size of the CBP tag itself is relatively small and is much less likely to affect the properties of the protein of interest, thus making this an appealing affinity tag in comparison to tags of larger sizes.

Advantages of CBP tag include its mild binding and elution conditions, which help to increase the ability of the fusion protein to maintain its native form after purification. CBP-fused proteins are eluted with a strip of calcium from the environment under very moderate buffer conditions (e.g., 2 mM EGTA, pH 8.0).

References

Zhao X, Li G, Liang S. Several affinity tags commonly used in chromatographic purification[J]. J Anal Methods Chem. December 2013.

P. Vaillancourt, C.F. Zheng, D.Q. Hoang, L. Breister, Affinity purification of recombinant proteins fused to calmodulin or to calmodulin-binding peptides, Methods Enzymol. 326 (2003) 340– 362.

W. Klein, Calmodulin-binding peptide as a removable affinity tag for protein purification, Methods. Mol. Biol. 205 (2000) 79–97.

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Target	Cat. No.	Product Name	Host	Isotype	Application	Inquiry
CBP-Tag	CABT-BL8709	Anti-Calmodulin Binding Peptide polyclonal antibody	Rabbit	IgG	ELISA, IP, WB	Inquiry
	CABT-BL8710	Anti-Calmodulin Binding Peptide polyclonal antibody [Biotin]	Rabbit	IgG	ELISA, IHC, WB	Inquiry
	CABT-BL8712	Anti-Calmodulin Binding Peptide polyclonal antibody [HRP]	Rabbit	IgG	ELISA, IHC, WB	Inquiry
	DPATB-H81312	Anti-CBP tag antibody	Rabbit	IgG	WB	Inquiry
	CABT-BL8711	Anti-Calmodulin Binding Peptide polyclonal antibody [FITC]	Rabbit	IgG	IF, IHC, WB	Inquiry
	CABT-Z372M	Mouse Anti-CBP Tag Monoclonal Antibody, clone 2E22F6	Mouse	IgG2b, κ	WB, IP, ELISA	Inquiry

CBP Tag Overview

Introduction to CBP tag

CBP tag for protein purification

Advantages of CBP tag

References

CBP Tag Antibodies