Can I use an IgG-HRP antibody with TAP-tagged yeast?

The TAP tag consists of protein A and calmodulin binding domain Since any IgG can bind to protein A, it can serve as the primary antibody. This does not mean that you can also use IgG-HRP as both primary and secondary antibodies however. Your IgG-HRP antibody should work for most applications with the TAP tagged strains. However, if you are using this in a Western Blot, the protein will be denatured so the antibody will most likely not bind.