Enthalpic destabilization of a mutant human lysozyme lacking a disulfide bridge between cysteine-77 and cysteine-95.


To understand the role of disulfide bridges in protein stability, the thermodynamic changes in the denaturation of two mutant human lysozymes lacking a disulfide bridge between Cys-77 and Cys-95 (C77A and C77/95A) were analyzed using differential scanning calorimetry (DSC). At pH 3.0 and 57 degrees C, the stabilities of both the C77A and C77/95A mutants were decreased about 4.6 kcal.mol-1 in Gibbs free energy change. Under the same conditions, the enthalpy changes (delta H) were 94.8 and 90.8 kcal.mol-1, respectively, which were smaller than that of the wild type (100.8 kcal.mol-1). The destabilization of the mutants was caused by enthalpic factors. Although X-ray crystallography indicated that the mutants preserve the wild-type tertiary structure, removal of the disulfide bridge increased the flexibility of the native state of the mutants. This was indicated both by an increase in the crystallographic thermal factors (B-factors) and by a decrease in the affinity of N-acetylglucosamine trimer [(NAG)3] observed using isothermal titration calorimetry (DTC) due to entropic effects. Thus, the effect of cross-linking on the stability of a protein is not solely explained by the entropy change in denaturation. Study holds ProTherm entries: 105, 106, 2155, 11765, 13945 Extra Details: human lysozyme; enthalpic destabilization; protein stability;,differential scanning calorimetry; entropic effects

Submission Details

ID: An4QoHnP

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:14 p.m.

Version: 1

Publication Details
Kuroki R;Inaka K;Taniyama Y;Kidokoro S;Matsushima M;Kikuchi M;Yutani K,Biochemistry (1992) Enthalpic destabilization of a mutant human lysozyme lacking a disulfide bridge between cysteine-77 and cysteine-95. PMID:1525170
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 Lysozyme C P61626 LYSC_HUMAN
100.0 Lysozyme C P61627 LYSC_PANPA
100.0 Lysozyme C P61628 LYSC_PANTR
100.0 Lysozyme C P79179 LYSC_GORGO
99.2 Lysozyme C P79239 LYSC_PONPY
96.9 Lysozyme C P79180 LYSC_HYLLA