Major intrinsic polypeptide (MIP26K) from lens membrane: reconstitution into vesicles and inhibition of channel forming activity by peptide antiserum.

Bovine and human lens membrane, when reconstituted into lipid vesicles containing oxidized cytochrome C, will mediate the transmembrane passage of ascorbate into the vesicles, where the reduction of cytochrome C is measured spectrophotometrically. This channel forming activity is specifically inhibited by antiserum made against a synthetic octapeptide near the C-terminus of MIP26K. Together, these studies describe a direct and more sensitive assay system for measurement of channel-forming activity of MIP26K, and suggest that the C-terminus of this molecule may be particularly important in the regulation of channel formation.