1Q5I

Crystal structure of bacteriorhodopsin mutant P186A crystallized from bicelles

Summary for 1Q5I

• Entry DOI: 10.2210/pdb1q5i/pdb
• Related: 1Q5J
• Descriptor: Bacteriorhodopsin, RETINAL (3 entities in total)
• Functional Keywords: alpha helix, membrane protein
• Biological source: Halobacterium salinarum
• Cellular location: Cell membrane ; Multi-pass membrane protein : P02945
• Total number of polymer chains: 2
• Total formula weight: 54375.80

Authors

Yohannan, S.,Faham, S.,Yang, D.,Whitelegge, J.P.,Bowie, J.U. (deposition date: 2003-08-07, release date: 2004-01-06, Last modification date: 2024-10-09)

Primary citation

Yohannan, S.,Faham, S.,Yang, D.,Whitelegge, J.P.,Bowie, J.U.
The evolution of transmembrane helix kinks and the structural diversity of G protein-coupled receptors.
Proc.Natl.Acad.Sci.USA, 101:959-963, 2004

PubMed Abstract: One of the hallmarks of membrane protein structure is the high frequency of transmembrane helix kinks, which commonly occur at proline residues. Because the proline side chain usually precludes normal helix geometry, it is reasonable to expect that proline residues generate these kinks. We observe, however, that the three prolines in bacteriorhodopsin transmembrane helices can be changed to alanine with little structural consequences. This finding leads to a conundrum: if proline is not required for helix bending, why are prolines commonly present at bends in transmembrane helices? We propose an evolutionary hypothesis in which a mutation to proline initially induces the kink. The resulting packing defects are later repaired by further mutation, thereby locking the kink in the structure. Thus, most prolines in extant proteins can be removed without major structural consequences. We further propose that nonproline kinks are places where vestigial prolines were later removed during evolution. Consistent with this hypothesis, at 14 of 17 nonproline kinks in membrane proteins of known structure, we find prolines in homologous sequences. Our analysis allows us to predict kink positions with >90% reliability. Kink prediction indicates that different G protein-coupled receptor proteins have different kink patterns and therefore different structures.

PubMed: 14732697
DOI: 10.1073/pnas.0306077101

Experimental method

X-RAY DIFFRACTION (2.3 Å)