Structures of randomly generated mutants of T4 lysozyme show that protein stability can be enhanced by relaxation of strain and by improved hydrogen bonding via bound solvent.


The structures of three mutants of bacteriophage T4 lysozyme selected using a screen designed to identify thermostable variants are described. Each of the mutants has a substitution involving threonine. Two of the variants, Thr 26-->Ser (T26S) and Thr 151-->Ser (T151S), have increased reversible melting temperatures with respect to the wild-type protein. The third, Ala 93-->Thr (A93T), has essentially the same stability as wild type. Thr 26 is in the wall of the active-site cleft. Its replacement with serine results in the rearrangement of nearby residues, most notably Tyr 18, suggesting that the increase in stability may result from the removal of strain. Thr 151 in the wild-type structure is far from the active site and appears to sterically prevent the access of solvent to a preformed binding site. In the mutant, the removal of the methyl group allows access to the solvent binding site and, in addition, the Ser 151 hydroxyl rotates to a new position so that it also contributes to solvent binding. Residue 93 is in a highly exposed site on the surface of the molecule, and presumably is equally solvent exposed in the unfolded protein. It is, therefore, not surprising that the substitution Ala 93-->Thr does not change stability. The mutant structures show how chemically similar mutations can have different effects on both the structure and stability of the protein, depending on the structural context. The results also illustrate the power of random mutagenesis in obtaining variants with a desired phenotype.(ABSTRACT TRUNCATED AT 250 WORDS) Study holds ProTherm entries: 1497, 1498, 1499, 1500 Extra Details: cysteine-free pseudo wild type lysozyme, 1L63 (C54T, C97A) mutagenesis; prediction; structural context; thermostability

Submission Details

ID: 7gxbRqyH4

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:17 p.m.

Version: 1

Publication Details
Pjura P;Matthews BW,Protein Sci. (1993) Structures of randomly generated mutants of T4 lysozyme show that protein stability can be enhanced by relaxation of strain and by improved hydrogen bonding via bound solvent. PMID:8298466
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
3EML 2008-09-24T00:00:00+0000 2.6 The 2.6 A Crystal Structure of a Human A2A Adenosine Receptor bound to ZM241385.
3SB8 2011-06-03T00:00:00+0000 2.65 Cu-mediated Dimer of T4 Lysozyme D61H/K65H by Synthetic Symmetrization
5JWW 2016-05-12T00:00:00+0000 1.47 T4 Lysozyme L99A/M102Q with 1-Hydro-2-ethyl-1,2-azaborine Bound
3SB9 2011-06-03T00:00:00+0000 2.45 Cu-mediated Dimer of T4 Lysozyme R76H/R80H by Synthetic Symmetrization
5YQR 2017-11-07T00:00:00+0000 2.4 Crystal structure of the PH-like domain of Lam6
1CTW 1999-08-20T00:00:00+0000 2.1 T4 LYSOZYME MUTANT I78A
3SN6 2011-06-28T00:00:00+0000 3.2 Crystal structure of the beta2 adrenergic receptor-Gs protein complex
2RBQ 2007-09-19T00:00:00+0000 1.63 3-methylbenzylazide in complex with T4 L99A/M102Q
1T8F 2004-05-12T00:00:00+0000 2.15 Crystal structure of phage T4 lysozyme mutant R14A/K16A/I17A/K19A/T21A/E22A/C54T/C97A
3CDV 2008-02-27T00:00:00+0000 1.73 Contributions of all 20 amino acids at site 96 to the stability and structure of T4 lysozyme

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Endolysin P00720 ENLYS_BPT4