G proteins are so-called because they bind the guanine nucleotides GDP and GTP. They are heterotrimers (i.e., made of three different subunits) associated with. the inner surface of the plasma membrane and. transmembrane receptors of hormones, etc. These are called G protein-coupled receptors (GPCRs).
Apply the metal paint to the mailbox in slow and even sections. Be sure to cover every inch of the metal mailbox including the door, hanging lip and the back. When this layer is dry remove the tape from the mailbox flag.
2. Sand the cast iron with a medium-grit sandpaper or steel wool until the paint and rust are gone. You can complete this process by hand, using a circular rubbing motion.Alternately, use an electric sander or a handheld rotary tool with a sanding wheel attachment for tight spaces.ast iron needs a layer of protection, such as a coat of paint, polyurethane, wax or oil, against moisture and humidity. Without such protection the metal quickly rusts. It's important to remove layers of old paint and rust just prior to refinishing so that the new layer of protection can be applied immediately.