We characterized two mutations in KCNJ2 leading to Andersen syndrome. Both mutations arose de-novo, causing the amino acid exchanges Y68D or D78Y in the N-terminal slide helix of the Kir2.1 potassium channel. HA-epitope tagged mutant Kir2.1 proteins reached the plasma membrane of oocytes, but were non- functional. Co-expression of mutant Kir2.1 subunits with wild- type Kir2.x in oocytes had a dominant-negative effect. Voltage clamp and fluorescence measurements in HEK293 cells confirmed these findings. Wild-type Kir2.1-DsRed and mutant Kir2.1-EGFP co-localized in the plasma membrane. Y68D, D78Y and several previously reported AS mutations are clustered on the hydrophilic, cytosolic side of the slide helix and showed normal trafficking to the plasma membrane. Using an in-vitro lipid binding assay we found that mutant Y68D or D78Y N-terminal peptides bind PIP2 similar to wild type. Yeast two hybrid analysis showed that AS-associated mutations in the slide helix and C- terminus disturb the interaction between the two regions. Our findings suggest that the hydrophilic side of the slide helix interacts with a specific domain of the C-terminus facing the membrane. This interaction may be required for normal gating, both in homomeric and heteromeric Kir2 channels, and is disturbed in several mutations causing Andersen syndrome.