Iodination of rhodopsin and transmembrane topology

Since most intact cells or sealed membrane vesicles are impermeable to lactoperoxidase (MW 78,000), the enzymatic iodination technique is ideally suited for probing the spatial arrangement of proteins in membranes. Using this procedure, it was posible to demonstrate that rhodopsin is a transmembrane protein: Although a detailed account of this approach has already been published, it is useful to provide a concise summary of the experimental details that may aid others attempting to use or extend the same procedure.