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.
But the main issue is providing protection for your steel door. The type of paint you use depends on what type of paint is already on the door. Most people paint their doors with latex paint, but some of us do it the hard way and use oil-based paint, such as simple spray cans (tricky because of the overspray) or a quart can of oil-based paint like Rust-Oleum.