Transition state of the rate-limiting step of heat denaturation of Cry3A delta-endotoxin.


Heat denaturation of Cry3A delta-endotoxin from Bacillus thuringiensis var. tenebrionis and its 55 kDa fragment was studied by differential scanning microcalorimetry at low pH. Analysis of the calorimetric data has shown that denaturation of Cry3A delta-endotoxin is a nonequilibrium process at heating rates from 0. 125 to 2 K/min. This means that the stability of delta-endotoxin (the apparent temperature of denaturation Tm) under these conditions is under kinetic control rather than under thermodynamic control. It has been shown that heat denaturation of this protein is a one-step kinetic process. The enthalpy of the process and its activation energy were measured as functions of temperature. The data obtained allow confirmation of the fact that the conformation of delta-endotoxin at the transition state only slightly differs from its native conformation with respect to compactness and extent of hydration. The comparison of the activation energy for intact delta-endotoxin and the 55 kDa fragment showed that the transition of the molecule to a transition state does not cause any changes in the conformation of three N-terminal alpha-helices. Complete removal of the N-terminal domain of delta-endotoxin and 40 amino acids from the C-terminus beta-sheet domain III causes an irreversible loss of the tertiary structure. Thus, during protein folding the nucleation core determining protein stability does not involve its three initial alpha-helices but may include the remaining alpha-helices of the N-terminal domain. The functional significance of peculiarities of structure arrangement of the delta-endotoxin molecule is discussed. Study holds ProTherm entries: 16310, 16311, 16312, 16313, 16314, 16315, 16316, 16317, 16318, 16319, 16320, 16321, 16322 Extra Details: Scanning rate V=1.00 K/min Cry3A delta-endotoxin, one-step kinetic, heat denaturation

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:47 p.m.

Version: 1

Publication Details
Potekhin SA;Loseva OI;Tiktopulo EI;Dobritsa AP,Biochemistry (1999) Transition state of the rate-limiting step of heat denaturation of Cry3A delta-endotoxin. PMID:10194327
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 Pesticidal crystal protein Cry3Aa P0A381 CR3AA_BACTD
100.0 Pesticidal crystal protein Cry3Aa P0A380 CR3AA_BACTM
100.0 Pesticidal crystal protein Cry3Aa P0A379 CR3AA_BACTT