Tagging at the N-terminus instead of the C-terminus greatly increases the risk of the protein not localizing correctly, due to masking of the signal sequence at the N-terminus. Tagging at the C-terminus is thus better for preserving localization; an exception to this, however, is for a handful proteins that localize to cell walls or the ER. These often contain C-terminal signal sequences, which can be interrupted by C-terminal tagging.