The role of ion channels in cell physiolo
gy is re
gulated by processes occurrin
g after proteinbiosynthesis, which are critical for both channel function and tar
getin
g of channels to appropriate cellcompartments. Here we apply biochemical and electrophysiolo
gical methods to investi
gate the role of thehi
gh-conductance, calcium-activated potassium (Maxi-K) channel C-terminal domain in channel tetramerization, association with the
![](/ima<font color=)
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">1 subunit, traffickin
g of the channel complex to the cell surface, and channelfunction. No evidence for channel tetramerization, cell surface expression, or function was observed withMaxi-K
1-323, a construct truncated three residues after the S
6 transmembrane domain. However, Maxi-K
1-343 and Maxi-K
1-441 are able to form tetramers and to associate with the
![](/ima<font color=)
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">1 subunit. Maxi-K
1-343-
![](/ima<font color=)
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">1and Maxi-K
1-441-
![](/ima<font color=)
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">1 complexes are efficiently tar
geted to the cell surface and cannot be pharmacolo
gicallydistin
guished from full-len
gth channels in bindin
g experiments but do not form functional channels. Maxi-K
1-651 forms tetramers and associates with
![](/ima<font color=)
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">1; however, the complex is not present at the cell surface,but is retained intracellularly. Maxi-K
1-651 surface expression and channel function can be fully rescuedafter coexpression with its C-terminal complement, Maxi-K
652-1113. However coexpression of Maxi-K
1-343and Maxi-K
1-441 with their respective C-terminal complements did not rescue channel function. To
gether,these data demonstrate that the domain(s) in the Maxi-K channel necessary for formation of tetramers,coassembly with the
![](/ima<font color=)
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle">1 subunit, and cell surface expression resides within the S
0-S
6 linker domain ofthe protein, and that structural constraints within the
gatin
g rin
g in the C-terminal re
gion can re
gulatetraffickin
g and function of constructs truncated in this re
gion.