Affinity Tag Antibodies for Detecting and Studying Tagged Proteins

An affinity tag antibody recognizes an engineered peptide sequence or fusion protein attached to a recombinant target. Examples include His, FLAG, HA, Myc, GST, V5 and Strep tags. Recognition depends on the exact tag sequence and whether that sequence remains accessible under the conditions used in the experiment.

A protein-specific antibody recognizes an epitope belonging to the native target protein. A tag antibody instead recognizes an engineered sequence added to the construct. Tag antibodies are useful when no reliable antibody exists for the native protein or when the same detection system is needed across multiple recombinant targets.

It can be used for both only when the individual antibody has been validated for both methods. Western blotting usually presents a denatured target, while immunoprecipitation requires recognition of a tag exposed on a native or partially folded protein. Always review the product's application data before selection.

The tag may become exposed after denaturation but remain buried within the native protein or protein complex. Other possible causes include insufficient expression, unsuitable lysis conditions, weak antibody binding, excessive washing, steric hindrance or an antibody that has not been validated for immunoprecipitation.

Yes. Tag position can influence accessibility because either terminus may be buried by protein folding, membrane association or interactions with other molecules. A tag can also be removed by proteolytic processing. Testing an alternative position or adding an appropriate linker may improve recognition, depending on the construct.

Monoclonal antibodies recognize a defined epitope and generally provide consistent recognition between experiments and production lots. Polyclonal antibodies contain multiple antibody populations and may produce stronger detection under some conditions. The better option depends on the application, background tolerance, required consistency and accessibility of the tag.

A directly conjugated antibody is useful when you want to shorten the workflow, avoid a secondary antibody or include the tagged protein in a multiplex experiment. The selected enzyme or fluorophore must be compatible with the detection equipment, other labels in the experiment and the expected abundance of the target.

Include an untransfected or untagged sample as a negative control and, when possible, a known tagged construct as a positive control. Imaging and flow experiments may also require secondary-only, unstained, single-color or isotype controls. A loading or expression control is useful when comparing samples by Western blotting.