The Secret Lives of Proteins

The Secret Lives of Proteins Recent research suggests that many structural and enzymatic proteins serve double or even triple duty (see Enzymatic Alter-Egos Unmasked). Three multifunctional proteins identified in higher animals are shown below. Gephyrin Proposed functions: ©2003 American Society for Biochemistry & Molecular Biology  Trimeric structure of gephyrin's N-terminal domain in rat. Secondary structural elements are labeled for one monomer. Black arrows indicate the po

October 6, 2003

The Secret Lives of Proteins

Recent research suggests that many structural and enzymatic proteins serve double or even triple duty (see Enzymatic Alter-Egos Unmasked). Three multifunctional proteins identified in higher animals are shown below.

Gephyrin

Proposed functions:

©2003 American Society for Biochemistry & Molecular Biology
 Trimeric structure of gephyrin's N-terminal domain in rat. Secondary structural elements are labeled for one monomer. Black arrows indicate the positions of proposed active sites. (M. Sola et al., J Biol Chem, 276:25294-301, 2001)

  • In neurons, forms a scaffold that stabilizes inhibitory neurotransmitter receptors by anchoring them to the cytoskeleton
  • Involved in synthesizing the molybdenum cofactor (Moco), a crucial component of certain enzymes that catalyze redox reactions
  • May regulate translational machinery synthesizing proteins in dendrites
  • May link neurotransmitter receptors to intracellular signaling proteins that regulate long-term synaptic changes (which underlie learning and memory)

 

Wiskott-Aldrich Syndrome Protein (WASP)

Proposed functions:

© Nature
 Two views of a WASP GTPase binding domain, which is involved in the protein's autoinhibitory function. Side-chain residues whose mutation is associated with disease are shown. (A.S. Kim et al., Nature, 404:151-8, 2000)

  • Aids in macrophage phagocytosis of apoptotic cells
  • Organizes actin skeletons in immune cells
  • Serves in interactions in which T cells aid in the functioning of B cells

 

Phosphoglucose Isomerase (PGI)

Proposed functions:

©2003 American Society for Biochemistry & Molecular Biology
 The PGI dimer. One molecule is red and gold while the other is green and purple. Protein inhibitors 5-phospho-D-arabinonate and N-bromoacetylethanolamine phosphate are cyan and dark blue, respectively. (Image from C.C. Chou et al., J Biol Chem, 275:23154-60, 2000)

  • Catalyzes a step in glycolysis
  • Stimulates differentiation in myeloid leukemia cells
  • Carries signals that aid B-cell maturation
  • Functions as a nerve growth factor
  • Mediates migration in tumor and other cells

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