Published Online: 16 APR 2012
Copyright © 2001 John Wiley & Sons, Ltd. All rights reserved.
How to Cite
Ramasarma, T., Joshi, N., Sekar, K., Uthayakumar, M. and Sherlin, D. 2012. Transmembrane Domains. eLS. .
- Published Online: 16 APR 2012
Stretches of approximately 25 hydrophobic residues with an occasional polar residue of integral proteins that pass across membrane are known as transmembrane (TM) domains. Besides anchoring to the membrane they participate in the functions of these proteins in some unspecified way. A variety of membrane proteins with spans in the range 1–17 are present in human genome and those with 1, 4 and 7 spans are more common. Impacting a variety of cellular functions, these include receptors for growth factors, hormones and other ligands, two-way membrane transporters, selective enzymes, channel proteins, energy-transducing tiny molecular motor, molecular facilitators in signalling, adhesion, differentiation and proliferation. Highly variable sequences of these short stretches of hydrophobic residues of TM domains, with hardly any repetition, arise out of repeating XTX/XCX triplets in their complementary deoxyribonucleic acid (cDNA). They are encoded by a random exon make-up, one exon coding for one or more domains and one domain coded by two exons with the junction between triplets and in some cases within a triplet.
Cell membrane is composed of hydrophobic phospholipid bilayer that separates two aqueous phases.
The selective permeability endows the membrane two-way transport of desired materials.
Proteins attached to the membrane facilitate this exchange process.
Proteins that span across the bilayer in one or multiple passes are known as integral proteins or transmembrane (TM) proteins.
TM domains, composed of largely hydrophobic residues, anchor these proteins firmly to the membrane and also participate in the functions.
Topology of TM domains facilitates transfer of signals, channelling ions and transporting material.
The amino acid sequences of TM domains are highly variable and are not repeated.
Some of these short stretches of TM domains are encoded by two exons with junction between triplet or within triplet.
- transmembrane domains;
- membrane anchors;
- exon distribution;
- XTX/XCX-enriched exons