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Definition

noun, plural: transmembrane proteins

A protein that spans the entire biological membrane.

Supplement

Transmembrane proteins may be classified in two major groups:

• Alpha-helix - present in all types of biological membranes.
• Beta barrel - present in outer membranes of Gram-negative bacteria, cell wall of Gram-positive bacteria, outer membranes of mitochondria and chloroplasts.

Word origin: L, comb. form of trāns (adv. and prep.) across, beyond, through + -membrane.

Acronym: TM.

See also: porin, ion channel.