The tyrosine corner: a feature of most Greek key beta-barrel proteins

Protein Sci. 1994 Nov;3(11):1927-37. doi: 10.1002/pro.5560031104.


The Tyr corner is a conformation in which a tyrosine (residue "Y") near the beginning or end of an antiparallel beta-strand makes an H bond from its side-chain OH group to the backbone NH and/or CO of residue Y - 3, Y - 4, or Y - 5 in the nearby connection. The most common "classic" case is a delta 4 Tyr corner (more than 40 examples listed), in which the H bond is to residue Y - 4 and the Tyr chi 1 is near -60 degrees. Y - 2 is almost always a glycine, whose left-handed beta or very extended beta conformation helps the backbone curve around the Tyr ring. Residue Y - 3 is in polyproline II conformation (often Pro), and residue Y - 5 is usually a hydrophobic (often Leu) that packs next to the Tyr ring. The consensus sequence, then, is LxPGxY, where the first x (the H-bonding position) is hydrophilic. Residues Y and Y - 2 both form narrow pairs of beta-sheet H-bonds with the neighboring strand. delta 5 Tyr corners have a 1-residue insertion between the Gly and Tyr, forming a beta-bulge. One protein family has a delta 4 corner formed by a His rather than a Tyr, and several examples use Trp in place of Tyr. For almost all these cases, the protein or domain is a Greek key beta-barrel structure, the Tyr corner ends a Greek key connection, and it is well-conserved in related proteins. Most low-twist Greek key beta-barrels have 1 Tyr corner. "Reverse" delta 4 Tyr corners (H bonded to Y + 4) and other variants are described, all less common and less conserved. It seems likely that the more classic Tyr corners (delta 4, delta 5, and delta 3 Tyr, Trp, or His) contribute to the stability of a Greek key connection over a hairpin connection, and also that they may aid in the process of folding up Greek key structures.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Azurin / chemistry
  • Bacterial Proteins / chemistry
  • Crystallins / chemistry
  • Fibronectins / chemistry
  • Hydrogen Bonding
  • Immunoglobulins / chemistry
  • Molecular Sequence Data
  • Prealbumin / chemistry
  • Protein Conformation*
  • Protein Folding*
  • Protein Structure, Secondary*
  • Superoxide Dismutase / chemistry
  • Tyrosine / chemistry*
  • Zinostatin / chemistry


  • Bacterial Proteins
  • Crystallins
  • Fibronectins
  • Immunoglobulins
  • Prealbumin
  • mauC protein, Methylobacterium extorquens
  • Azurin
  • Tyrosine
  • Zinostatin
  • Superoxide Dismutase