1S51

Thr24Ser Bacteriorhodopsin

Summary for 1S51

• Entry DOI: 10.2210/pdb1s51/pdb
• Related: 1S52 1S53 1S54
• Descriptor: bacteriorhodopsin, RETINAL (3 entities in total)
• Functional Keywords: membrane protein; bacteriorhodopsin, proton transport
• Biological source: Halobacterium salinarum
• Cellular location: Cell membrane; Multi-pass membrane protein: P02945
• Total number of polymer chains: 2
• Total formula weight: 50263.66

Authors

Yohannan, S.,Faham, S.,Yang, D.,Grosfeld, D.,Chamberlain, A.K.,Bowie, J.U. (deposition date: 2004-01-19, release date: 2004-03-02, Last modification date: 2024-11-06)

Primary citation

Yohannan, S.,Faham, S.,Yang, D.,Grosfeld, D.,Chamberlain, A.K.,Bowie, J.U.
A C(alpha)-H.O Hydrogen Bond in a Membrane Protein Is Not Stabilizing
J.Am.Chem.Soc., 126:2284-2285, 2004

PubMed Abstract: Hydrogen bonds involving a carbon donor are very common in protein structures, and energy calculations suggest that Calpha-H...O hydrogen bonds could be about one-half the strength of traditional hydrogen bonds. It has therefore been proposed that these nontraditional hydrogen bonds could be a significant factor in stabilizing proteins, particularly membrane proteins as there is a low dielectric and no competition from water in the bilayer core. Nevertheless, this proposition has never been tested experimentally. Here, we report an experimental test of the significance of Calpha-H...O bonds for protein stability. Thr24 in bacteriorhodopsin, which makes an interhelical Calpha-H...O hydrogen bond to the Calpha of Ala51, was changed to Ala, Val, and Ser, and the thermodynamic stability of the mutants was measured. None of the mutants had significantly reduced stability. In fact, T24A was more stable than the wild-type protein by 0.6 kcal/mol. Crystal structures were determined for each of the mutants, and, while some structural changes were seen for T24S and T24V, T24A showed essentially no apparent structural alteration that could account for the increased stability. Thus, Thr24 appears to destabilize the protein rather than stabilize. Our results suggest that Calpha-H...O bonds are not a major contributor to protein stability.

PubMed: 14982414
DOI: 10.1021/ja0317574

Experimental method

X-RAY DIFFRACTION (2 Å)