transmembrane adhesion proteins Cytoskeletonlinked transmembrane molecules with one end linking to the cytoskeleton inside the cell and the other end linking to other structures outside it.
transmembrane protein   Membrane protein that extends through the lipid bilayer, with part of its mass on either side of the membrane. (Figure 10–17) transmitter-gated ion channel (ion-channel-coupled receptor, ionotropic receptor) Ion channel found at chemical synapses in the postsynaptic plasma membranes of nerve and muscle cells. Opens only in response to the binding of a specific extracellular neurotransmitter. The resulting inflow of ions leads to the generation of a local electrical signal in the postsynaptic cell. (Figures 11–36 and 15–6) transport vesicle Membrane-enclosed transport containers that bud from specialized coated regions of donor membrane and pass from one cell compartment to another as part of the cell’s membrane transport processes; vesicles can be spherical, tubular, or irregularly shaped.
transporter (carrier protein, permease) Membrane transport protein that binds to a solute and transports it across the membrane by undergoing a series of conformational changes. Transporters can transport ions or molecules passively down an electrochemical gradient or can link the conformational changes to a source of metabolic energy such as ATP hydrolysis to drive active transport. Compare channel protein. See also membrane transport protein. (Figure 11–3) transposable element (transposon) Segment of DNA that can move from one genome position to another by transposition. (Table 5–4, p. 288) transposition (transpositional recombination) Movement of a DNA sequence from one genome site to another.  (Table 5–4, p. 288) treadmilling   Process by which a polymeric protein filament is maintained at constant length by addition of protein subunits at one end and loss of subunits at the other. (Panel 16–2,  pp. 902–903)
Trithorax group   Set of proteins critical for cell memory that maintains the transcription of Hox genes in cells where transcription has already been switched on.
t-SNAREs   Transmembrane SNARE protein, usually composed of three proteins and found on target membranes where it interacts with v-SNAREs on vesicle membranes.
tubulin   The protein subunit of microtubules. (Panel 16–1,  p. 891, and Figure 16–42) γ-tubulin ring complex (γ-TuRC) Protein complex containing γ-tubulin and other proteins that is an efficient nucleator of microtubules and caps their minus ends.
tumor progression   Process by which an initial mildly disordered cell behavior gradually evolves into a full-blown cancer. (Figures 20–8 and 20–9) tumor suppressor gene   Gene that appears to help prevent formation of a cancer. Loss-of-function mutations in such genes favor the development of cancer. (Figure 20–17) tumor virus   Virus that can help make the cell it infects cancerous.
turgor pressure   Large hydrostatic pressure developed inside a plant cell as the result of the intake of water by osmosis; it is the force driving cell expansion in plant growth and it maintains the rigidity of plant stems and leaves.
two-dimensional gel electrophoresis   Technique combining two different separation procedures—separation by charge (isoelectric focusing) in the first dimension, then separation by size in a direction at a right angle to that of the first step—to resolve up to 2000 proteins in the form of a two-dimensional protein map.
type III fibronectin repeat   The major repeat domain in fibronectin, it is about 90 amino acids long and occurs at least 15 times in each subunit. The repeat is among the most common of all protein domains in vertebrates.