Published Online: 15 SEP 2006
Copyright © 2006 Wiley-VCH Verlag GmbH & Co. KGaA
Encyclopedia of Molecular Cell Biology and Molecular Medicine
How to Cite
Dakshinamurti, K. 2006. Vitamin Receptors. Encyclopedia of Molecular Cell Biology and Molecular Medicine. .
- Published Online: 15 SEP 2006
Interlocking ligand–receptor systems constitute an intra- and intercellular communication system in which exogenous or endogenous molecules such as vitamins, hormones, cytokines, and foreign macromolecules convey signals through association with membrane structures (i.e. receptors). Sequential interactions between ligands and receptors on membranes of cells or organelles coordinate metabolism within the same and between different cells and organs. Cell communication is regulated by activation events and by processes that limit such activation.
This article presents current information on the ligand (vitamin)-receptor (binding protein) interaction as it applies to vitamins, from the site of enteric absorption to the site of vitamin function. For the absorption and transport of most vitamins, specific proteins, which have a recognition factor incorporated into them, are involved. At the plasma membrane of the cell, a second recognition factor has to function before the vitamin is internalized. Intracellular vitamin-binding proteins and their interaction with cellular systems resulting in the biological action of the vitamins provide the last step in the successive stages of communication. Thus, we have the concept of a ligand (vitamin), an extraorganismic molecule, reacting with a specific protein entity, the receptor, facilitating absorption and transport of the ligand to its site of action with the resultant sequence of physiological events to which we refer as vitamin function. The term “receptor,” in the context of vitamins, refers to proteins with a recognition function, not to receptors in the traditional pharmacological sense. It includes proteins that bind to the vitamin ligand and function as extracellular or intracellular transporters as well as the smaller number of vitamin-binding nuclear proteins. In the latter case, vitamins might act as small molecular modulators of protein-DNA interaction, a situation analogous to that of some hormones. The designation “receptors” for these categories of vitamin-binding proteins appears to be appropriate inasmuch as it connotes a function more than ligand binding.
The transcriptional patterns of selected genes are often altered by external signals that the cell receives. Thus, changes in nutritional supplies can either induce or repress the transcription of specific genes or gene sets. In many cases, the regulation of transcription (up or down) is mediated by alterations in the availability of essential transcription factors or by change in the factors' ability to bind to specific regulatory sequence motifs.
- Response Element;
- Transcription Factor;