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A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain.TMDs may consist of one or several alpha-helices or a transmembrane beta barrel.Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in TMDs are often hydrophobic, although proteins such as membrane pumps and ion channels can contain polar residues.
ABC transporter transmembrane domain is the main transmembrane structural unit of ATP-binding cassette transporter proteins, consisting of six alpha helixes that traverse the plasma membrane. Many members of the ABC transporter family ( Pfam PF00005 ) have two such regions.
For example, the "unfolded" bacteriorhodopsin in SDS micelles has four transmembrane α-helices folded, while the rest of the protein is situated at the micelle-water interface and can adopt different types of non-native amphiphilic structures. Free energy differences between such detergent-denatured and native states are similar to stabilities ...
Tetraspanins are a family of membrane proteins found in all multicellular eukaryotes also referred to as the transmembrane 4 superfamily (TM4SF) proteins. These proteins have four transmembrane alpha-helices and two extracellular domains, one short (called the s mall e xtracellular d omain or l oop, SED/SEL or EC1) and one longer, typically 100 ...
In molecular biology, ATP-binding domain of ABC transporters is a water-soluble domain of transmembrane ABC transporters. ABC transporters belong to the ATP-Binding Cassette superfamily, which uses the hydrolysis of ATP to translocate a variety of compounds across biological membranes. ABC transporters are minimally constituted of two conserved ...
Eight transmembrane segments that form a channel and allow for Cu(I) to pass through the membrane; An ATP-binding domain; A large N-terminal cytosolic domain that contains six repeated Cu(I)-binding sites, each containing a GMTCXXC motif. Proposed structure of copper-transporting protein ATP7A. Many motifs in the ATP7A structure are conserved: [11]
The membrane-spanning segments, designated S1-S6, all take the form of alpha helices with specialized functions. The fifth and sixth transmembrane segments (S5 and S6) and pore loop serve the principal role of ion conduction, comprising the gate and pore of the channel, while S1-S4 serve as the voltage-sensing region.
The basic fold of the MFS transporter is built around 12, [4] or in some cases, 14 transmembrane helices [5] (TMH), with two 6- (or 7- ) helix bundles formed by the N and C terminal homologous domains [6] of the transporter which are connected by an extended cytoplasmic loop.