Transferrin is a complex blood plasma glycoprotein which is found naturally in the blood stream and is often located attached to developing red blood cells (Macedo, 2008). Transferrin functions in the transport of free iron in biological fluids such as blood. Transferrin molecules accomplish this through their capacity for each molecule to bind to two atoms of ferric iron (Fe3+). Once the iron is bound to a transferrin in the blood stream and it encounters a transferrin receptor, the molecule binds specifically to the receptor and is incorporated into the cell via a vesicle. Normally the cells with the most transferrin receptors are found in the liver, spleen, and bone marrow (Encyclopædia Britannica, 2012). Energy-dependent proton pumps then reduce the pH inside the vesicle by adding protons to make it between 5.5-5.0. At this pH, transferrin becomes denatured and releases the ferric iron into the cytoplasm of the cell (Aisen, 1978). This iron can then be used in the production of hemoglobin, the absence of which causes anemia. Thus, transferrin is part of a biological mechanism for maintaining homeostasis with regard to iron levels (Crichton, 1987).
An RNA ligand or aptamer would be medically useful in running diagnostics for determining present levels of transferrin in the body. This could lead to diagnosis of a rare genetic disorder associated with transferrin imbalance, otherwise known as atransferrinemia (Hicke, 2000). A transferrin aptamer could also be used to determine rates of production and/or loss of transferrin in the body and therefore diagnose the cause of reduced hemoglobin production.
Specific Aim 1: Selection of RNA aptamers against Transferrin using SELEX. Transferrin facilitates ferric iron transport in the blood. Low or decreased levels of Transferrin are known to cause reduction in hemoglobin production and thereby cause anemia. The selection of an RNA aptamer against transferrin would serve a medical purpose by providing information regarding blood transferrin levels.
|Figure 1.1 – The Transferrin specific aptamer will bind and mark the saturated Transferrin molecule, allowing diagnostics to be run to determine blood Transferrin levels|