Chapter 6.2: Signal Molecule Receptors Can Be Classified into Several Groups

Flashcards from Chapter 6.1 of Principles of Life, 3rd Edition.

Signal receptors

Proteins that bind a particular signal molecule

• Grouped on position of reversible ligand binding

• These utilize carbohydrate residues that affect folding

Intracellular receptors

Receptors located inside the cell that can bind to nonpolar substances

Membrane receptors

Transmembrane proteins with a ligand-binding and cytosolic region that initiates transduction and often functions as an enzyme

Signal regulation

Often performed through the production of competitive ligands

• Seen with caffeine and adenosine both binding to an adenosine-dependent drowsiness receptor

Ligand-gated ion channels

Channels that allow ions to pass through when activated by a ligand

• Seen with the acetylcholine receptor (AChR) requiring ACh to allow Na⁺ through

G proteins

Membrane proteins that can bind both the GDP and GTP molecules

G protein-coupled receptors (GPCRs)

Receptors that immediately activate G proteins in the cytosol

Heterotrimers

A GPCR-interacting G protein with three different monomers

• Has an alpha subunit that can bind GDP or GTP based on activation state, exchanging for GTP when activated

  • This causes an effector protein activation for further changes

Protein kinase receptors

Receptors that change shape upon binding, phosphorylating and exposing a cytosolic kinase enzyme

• These target the amino acids serine, threonine, and tyrosine

Autophosphorylation

The phosphorylation of a receptor’s own residues, particularly in kinase protein receptors

• Seen with the receptor for insulin, which binds, changes shape, does this, and triggers a response