EXPRESSION OF A MINIMAL K-CHANNEL PROTEIN IN MAMMALIAN-CELLS AND IMMUNOLOCALIZATION IN GUINEA-PIG HEART()

The minimal K+ channel protein (minK also called I(sK)) is structurall y dissimilar to other cloned voltage-gated ion channels. mink is a 15- kD polypeptide with only one potential transmembrane helix. Published data suggest that the current associated with minK expression in Xenop us oocytes may be related to the slow cardiac delayed rectifier K+ cur rent (I(Ks)). However, the fact that minK expression has been limited exclusively to Xenopus oocytes has caused continuing concern about the nature of this protein and its molecular link to known mammalian K+ c hannels. We report in the present study the first expression of minK a ctivity in transiently transfected mammalian (HEK 293) cells and demon strate that the characteristics of the expressed minK current are simi lar to those of I(Ks) recorded from guinea pig heart cells under simil ar experimental conditions. We also show that an antibody directed aga inst the minK channel protein reacts with a surface antigen on adult g uinea pig ventricular myocytes and sinoatrial nodal cells, where I(Ks) is the dominant outward K+ current. The data provide strong evidence that a minK-like protein underlies I(Ks).