Energetics of structural domains in alpha-lactalbumin.


alpha-Lactalbumin is a small, globular protein that is stabilized by four disulfide bonds and contains two structural domains. One of these domains is rich in alpha-helix (the alpha-domain) and has Cys 6-Cys 120 and Cys 28-Cys 111 disulfide bonds. The other domain is rich in beta-sheet (the beta-domain), has Cys 61-Cys 77 and Cys 73-Cys 91 disulfide bonds, and includes one calcium binding site. To investigate the interaction between domains, we studied derivatives of bovine alpha-lactalbumin differing in the number of disulfide bonds, using calorimetry and CD at different temperatures and solvent conditions. The three-disulfide form, having a reduced Cys 6-Cys 120 disulfide bond with carboxymethylated cysteines, is similar to intact alpha-lactalbumin in secondary and tertiary structure as judged by its ellipticity in the near and far UV. the two-disulfide form of alpha-lactalbumin, having reduced Cys 6-Cys 120 and Cys 28-Cys 111 disulfide bonds with carboxymethylated cysteines, retains about half the secondary and tertiary structure of the intact alpha-lactalbumin. The remaining structure is able to bind calcium and unfolds cooperatively upon heating, although at lower temperature and with significantly lower enthalpy and entropy. We conclude that, in the two disulfide form, alpha-lactalbumin retains its calcium-binding beta-domain, whereas the alpha-domain is unfolded. It appears that the beta-domain does not require alpha-domain to fold, but its structure is stabilized significantly by the presence of the adjacent folded alpha-domain. Study holds ProTherm entries: 10034, 10035, 10036, 10037, 10038 Extra Details: N-terminal lactalbumin. alfa-lactalubumin; calorimetry; disulfide bonds;,domains; ellipticity

Submission Details

ID: kCpEhZeZ3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:39 p.m.

Version: 1

Publication Details
Hendrix TM;Griko Y;Privalov P,Protein Sci. (1996) Energetics of structural domains in alpha-lactalbumin. PMID:8732764
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 Alpha-lactalbumin P00711 LALBA_BOVIN
99.3 Alpha-lactalbumin Q9TSR4 LALBA_BOSMU
98.6 Alpha-lactalbumin Q9TSN6 LALBA_BUBBU
97.2 Alpha-lactalbumin P09462 LALBA_SHEEP
95.1 Alpha-lactalbumin P00712 LALBA_CAPHI