Role of aromatic side chains in the folding and thermodynamic stability of integral membrane proteins.


Aromatic residues are frequently found in helical and beta-barrel integral membrane proteins enriched at the membrane-water interface. Although the importance of these residues in membrane protein folding has been rationalized by thermodynamic partition measurements using peptide model systems, their contribution to the stability of bona fide membrane proteins has never been demonstrated. Here, we have investigated the contribution of interfacial aromatic residues to the thermodynamic stability of the beta-barrel outer membrane protein OmpA from Escherichia coli in lipid bilayers by performing extensive mutagenesis and equilibrium folding experiments. Isolated interfacial tryptophanes contribute -2.0 kcal/mol, isolated interfacial tyrosines contribute -2.6 kcal/mol, and isolated interfacial phenylalanines contribute -1.0 kcal/mol to the stability of this protein. These values agree well with the prediction from the Wimley-White interfacial hydrophobicity scale, except for tyrosine residues, which contribute more than has been expected from the peptide models. Double mutant cycle analysis reveals that interactions between aromatic side chains become significant when their centroids are separated by less than 6 A but are nearly insignificant above 7 A. Aromatic-aromatic side chain interactions are on the order of -1.0 to -1.4 kcal/mol and do not appear to depend on the type of aromatic residue. These results suggest that the clustering of aromatic side chains at membrane interfaces provides an additional heretofore not yet recognized driving force for the folding and stability of integral membrane proteins. Study holds ProTherm entries: 25449, 25450, 25451, 25452, 25453, 25454, 25455, 25456, 25457, 25458, 25459, 25460, 25461, 25462, 25463, 25464, 25465, 25466, 25467, 25468 Extra Details: 1mM EDTA was added in the experiment aromatic side chain; thermodynamic stability; membrane protein

Submission Details

ID: m9MCkgc23

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:55 p.m.

Version: 1

Publication Details
Hong H;Park S;Jiménez RH;Rinehart D;Tamm LK,J. Am. Chem. Soc. (2007) Role of aromatic side chains in the folding and thermodynamic stability of integral membrane proteins. PMID:17564441
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Outer membrane protein A P0A911 OMPA_ECO57
100.0 Outer membrane protein A P0A910 OMPA_ECOLI
96.6 Outer membrane protein A P02935 OMPA_SHIDY
96.9 Outer membrane protein A B7LNW7 OMPA_ESCF3
91.7 Outer membrane protein A A0A2S4N3N0 OMPA_SHIFL
95.2 Outer membrane protein A P80444 OMPA_ACTLI
90.6 Outer membrane protein A Q8Z7S0 OMPA_SALTI
90.6 Outer membrane protein A P02936 OMPA_SALTY
95.9 Outer membrane protein A P0C8Z2 OMPA_ESCFE