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Another example of a uniporter mediated transport protein is microsomal triglyceride transfer protein (MTTP) who is responsible for catalyzing the assembly of the triglyceride rich lipoproteins as well mediating their release from the lumen of the endoplasmic reticulum. What is distinguishable about this specific transfer protein is that it requires the protein PRAP1 to bind to the lipoprotein to facilitate the transport of said lipoprotein. MTTP only recognizes the PRAP1-lipoprotein complex and only then will it catalyze the transport reaction. In a way, the PRAP1 protein acts as a signal for MTTP. The importance of such interactions implies that mediated transport is not only dependent on transmembrane proteins but can also require the presence of additional non-transmembrane proteins. For instance, studies show that in the absence of a fully functional PRAP1 protein, MTTP fails to transport specific lipoproteins across the endoplasmic reticulum membrane.

Mutations in Transport Proteins[edit]
The importance of mediated transport proteins is visualized with the presence of mutations that render the transport proteins nonfunctional. A prime example of this are mutations found within the Archain 1 gene which codes for the transport proteins COPI and COPII. The main function of these transport proteins is to facilitate the passage of molecules from the endoplasmic reticulum to the golgi apparatus, and vice versa. The mutated ARCN1 gene gives rise to abnormal COPI who fails to transport type I collagen and leads to the secretion of collagen. Due to the fact that type I collagen is the main ingredient of connective tissue, such mutations are the cause of numerous severe skeletal disorders such as osteogenesis imperfecta and cranio-lenticulo-sutural dysplasia. Various variations of these disorders are characterized by visible physical dysplasia. This example highlights the importance of transport proteins, not only as a means for the passage of specific molecules across a membrane, but for proper bodily development.