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 PDB Entries

Structure ID Release Date Resolution Structure Title
1G90 2000-11-21T00:00:00+0000 0 NMR Solution Structure of Outer Membrane Protein A Transmembrane Domain: 10 conformers
2GE4 2006-03-17T00:00:00+0000 0 High-resolution solution structure of outer membrane protein A transmembrane domain
2JMM 2006-11-20T00:00:00+0000 0 NMR solution structure of a minimal transmembrane beta-barrel platform protein
2MQE 2014-06-19T00:00:00+0000 0 Solution structure of Escherichia coli Outer membrane protein A C-terminal domain
3JBU 2015-10-16T00:00:00+0000 3.64 Mechanisms of Ribosome Stalling by SecM at Multiple Elongation Steps
3NB3 2010-06-02T00:00:00+0000 19.0 The host outer membrane proteins OmpA and OmpC are packed at specific sites in the Shigella phage Sf6 virion as structural components
5M2Q 2016-10-13T00:00:00+0000 1.7 Structure of cobinamide-bound BtuF mutant W66F, the periplasmic vitamin B12 binding protein in E.coli
6ITC 2018-11-21T00:00:00+0000 3.45 Structure of a substrate engaged SecA-SecY protein translocation machine

Relevant UniProtKB Entries

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