The dipole moments of membrane proteins: potassium channel proteins. II. T1 assembly. Search for the voltage sensor Original Research Article

The dipole moments of potassium channel protein (Kcsa) and β-subunits were discussed in the previous paper of this series [Takashima, Biophys. Chem. 94 (2001) 209–218]. While the dipole moment of β-subunits was found to be very large, the dipole moment of Kcsa turned out to be somewhat smaller than β-subunits. As the continuation of this work, the discussion of the present paper is focussed on the dipole moment of T1 assembly, another component of the K-channel. As discussed later, the calculation using the X-ray crystallographic data by MacKinnon et al., revealed an astoundingly large dipole moment for T1 assembly. The dipole moment of T1 assembly combined with the likewise large dipole moment of β-subunits amounts to a sufficient value to play an essential role as a voltage sensor of potassium channel.