Previously, it has been shown that deletion of the aminoterminal region of CNGB1 could partially restore expression of these CNGA1-∆CLZ-containing channels 21 , suggesting that the amino-terminal region of CNGB1 might be involved in the highaffinity association between CNGA1 and CNGB1 subunits. Alternatively, the amino-terminal region of CNGB1 could contain a trafficking signal for incorrectly assembled heteromeric CNG channels 21 . This trafficking signal could provide a mechanism for error-correction where channels with more than one CNGB1 subunit are either poorly trafficked to the plasma membrane or rapidly removed from the membrane.