Tanford crossing
The Tanfordübergang (engl. Transition Tanford ) referred to in the biochemistry a change in protein folding , more precisely to a shift in the conformation of the turns of a β-sheet from E to F in the protein lactoglobulin .
properties
In 1959, Charles Tanford (1921–2009) discovered a reversible conformational change in lactoglobulin by titration at a pH of 7.5. Lactoglobulin is one of the lipocalins and, with a length of 162 amino acids, has the protein structure of a β-barrel made of eight β-sheets. The amino acid glutamic acid at position 89 (E89 or Glu89 for short) is responsible for the shift . This has an unusually high pK s value of 7.4. In the deprotonated state of the acid (at higher pH values) the turn is positioned backwards and gives way to the inside of the barrel or goblet. Below the Tanford transition, glutamic acid 89 is pressed “down” over the cup via the hydrogen bond to serine 116, thereby closing the cup. In the deprotonated state of Glu89 there is a change in the GH turn, then the hydrogen bond breaks apart, the EF turn folds backwards and is exposed compared to the cup. In this state, lactoglobulin is able to bind the hydrophobic ligands in the hydrophobic pocket inside the cup .
literature
- Charles Tanford: How protein chemists learned about the hydrophobic factor ; In: Protein Sci. 1997 June; 6 (6): 1358-1366. PMC 2143727 (free full text)
- Bin Qin: Structure determination of bovine B-lactoglobulin variants A and B: the structural consequences of point mutations, the structural basis of the Tanford transition, the structural influence of ligand on bovine BLGA , Dissertation at Massey University, 1998.
Individual evidence
- ↑ K. Sakurai, Y. Goto: Dynamics and mechanism of the Tanford transition of bovine beta-lactoglobulin studied using heteronuclear NMR spectroscopy. In: J Mol Biol. (2006), Vol. 356, No. 2, pp. 483-496. PMID 16368109 .