Helical and expanded conformation of equine beta-lactoglobulin in the cold-denatured state.


Abstract

The thermal unfolding transition of equine beta-lactoglobulin (ELG) was investigated by circular dichroism (CD) over a temperature range of -15 degrees C to 85 degrees C. In the presence of 2 M urea, a cooperative unfolding transition was observed both with increasing and decreasing temperature. The CD spectrum indicated that the heat and cold-denatured states of ELG have substantial secondary structures but lack persistent tertiary packing of the side-chains. In order to clarify the relation between the heat or cold-denatured state and the acid-denatured (A) state characterized previously, we have attempted to observe the temperature dependence of the CD spectrum at pH 1.5. The CD spectrum in the heat-denatured state is similar to that in the A state. The CD spectrum in the A state does not change cooperatively with increasing temperature. These results indicate that the heat-denatured state and the A state are the same structural state. On the other hand, the CD intensity at acid pH cooperatively increased with decreasing temperature. The CD spectrum at low temperature and acid pH is consistent with that in the cold-denatured state. Therefore, the cold-denatured state is distinguished from the heat-denatured state or the A state, and ELG assumes a larger amount of non-native alpha-helices in the cold-denatured state. Small angle X-ray scattering and analytical ultracentrifugation have indicated that ELG assumes an expanded chain-like conformation in the cold-denatured state in contrast to the compact globular conformation in the A state. The relation between the molecular size and the helical content in the partially folded states is discussed. Study holds ProTherm entries: 19244, 19245, 19246, 19247, 19248, 19249, 19250, 19251, 19252, 19253, 19254, 19255, 19256, 19257, 19258 Extra Details: The solution contains 2 M urea. small-angle X-ray scattering; sedimentation coefficient; folding; molten globule; stability

Submission Details

ID: rSwPNvy3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:51 p.m.

Version: 1

Publication Details
Yamada Y;Yajima T;Fujiwara K;Arai M;Ito K;Shimizu A;Kihara H;Kuwajima K;Amemiya Y;Ikeguchi M,J. Mol. Biol. (2005) Helical and expanded conformation of equine beta-lactoglobulin in the cold-denatured state. PMID:15925384
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
3KZA 2010-12-22 2.0 Crystal structure of Gyuba, a patched chimera of b-lactglobulin

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
98.8 Beta-lactoglobulin-1 P13613 LACB1_EQUAS
100.0 Beta-lactoglobulin-1 P02758 LACB1_HORSE