Final answer:
Signal peptidase is the protein family not involved in the targeting of transport vesicles to membranes, as it functions in cleaving signal peptides, unlike SNAREs, Rabs, and tethering proteins which are directly involved in membrane targeting.
Step-by-step explanation:
The protein family not involved in directing transport vesicles to the target membrane is D. signal peptidase. Signal peptidases are involved in the cleavage of signal peptides during the maturation of proteins, especially in bacteria, where they assist in the secretion process by removing signal peptides as proteins pass through the plasma membrane. Unlike SNAREs, Rabs, and tethering proteins, which play vital roles in the recognition, docking, and fusion of transport vesicles to their target membranes, signal peptidases do not directly facilitate the transport vesicle targeting process.