Polar residues in the protein core of Escherichia coli thioredoxin are important for fold specificity.


Most globular proteins contain a core of hydrophobic residues that are inaccessible to solvent in the folded state. In general, polar residues in the core are thermodynamically unfavorable except when they are able to form intramolecular hydrogen bonds. Compared to hydrophobic interactions, polar interactions are more directional in character and may aid in fold specificity. In a survey of 263 globular protein structures, we found a strong positive correlation between the number of polar residues at core positions and protein size. To probe the importance of buried polar residues, we experimentally tested the effects of hydrophobic mutations at the five polar core residues in Escherichia coli thioredoxin. Proteins with single hydrophobic mutations (D26I, C32A, C35A, T66L, and T77V) all have cooperative unfolding transitions like the wild type (wt), as determined by chemical denaturation. Relative to wt, D26I is more stable while the other point mutants are less stable. The combined 5-fold mutant protein (IAALV) is less stable than wt and has an unfolding transition that is substantially less cooperative than that of wt. NMR spectra as well as amide deuterium exchange indicate that IAALV is likely sampling a number of low-energy structures in the folded state, suggesting that polar residues in the core are important for specifying a well-folded native structure. Study holds ProTherm entries: 11738, 11739, 11740, 11741, 11742, 11743, 11744, 11745, 11746, 11747, 11748, 11749 Extra Details: hydrogen bonds; hydrophobic interactions; cooperative; amide deuterium exchange

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:43 p.m.

Version: 1

Publication Details
Bolon DN;Mayo SL,Biochemistry (2001) Polar residues in the protein core of Escherichia coli thioredoxin are important for fold specificity. PMID:11513583
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 Thioredoxin 1 P0AA27 THIO_ECO57
100.0 Thioredoxin 1 P0AA26 THIO_ECOL6
100.0 Thioredoxin 1 P0AA25 THIO_ECOLI
100.0 Thioredoxin 1 P0AA29 THIO_SALTI
100.0 Thioredoxin 1 P0AA28 THIO_SALTY
100.0 Thioredoxin 1 P0AA30 THIO_SHIFL