Question

Imagine a transmembrane protein made of 7 alpha helices. This protein functions as a pore that allows Cl- ions to pass through the membrane. Each alpha helix has hydrophobic amino acids on one surface and hydrophilic amino acids on the opposite surface. Describe how these helices are likely arranged in the membrane.

Answer 1

Hydrophobicity and hydrophillicity are very important in passage of ions through the membranes and arrangement of amino acids on the two side of membrane forms a gradient for passing the various types of ions. As chlorine is negative in charge so porin should maintain a net positive charge on the surface of membrane hence aminoacid like arginine, lysine and leucine which are basib and maintain positive charge are on outer surface and other hydrophilic amino acids are on inner side.