pH-dependent stability of the human alpha-lactalbumin molten globule state: contrasting roles of the 6 - 120 disulfide and the beta-subdomain at low and neutral pH.


Abstract

Many proteins are capable of populating partially folded states known as molten globule states. Alpha-lactalbumin forms a molten globule under a range of conditions including low pH (the A-state) and at neutral pH in the absence of Ca(2+) with modest amounts of denaturant. The A-state is the most thoroughly characterized and thought to mimic a kinetic intermediate populated during refolding at neutral pH. We demonstrate that the properties and interactions that stabilize the A-state and the pH 7 molten globule of human alpha-lactalbumin differ. The unfolding of the wild-type protein is compared to the unfolding of a variant that lacks the 6 - 120 disulfide bond and to an autonomously folded peptide construct that we have previously shown represents the minimum core structure of the A-state of human alpha-lactalbumin. Studies conducted at pH 2 and 7 show that the disulfide makes little contribution to the stability of the molten globule at pH 7 but is important at pH 2. In contrast, the beta-subdomain of the protein is less important at pH 2 than at pH 7. The role of helix propensity in stabilizing the different forms of the molten globule state is examined and it is shown that it cannot account for the differences. The strikingly different behavior observed at pH 2 and 7 indicates that the A-state may not be a rigorous mimic of the folding intermediate populated at pH 7. Study holds ProTherm entries: 16192, 16193, 16194, 16195, 16196, 16197, 16198, 16199, 16200, 16201, 16202, 16203, 16204, 16205 Extra Details: (i) 1mM EDTA was added in the experiment protein folding; alpha-lactalbumin; molten globule state; protein stability; pH effects

Submission Details

ID: RserXM9d3

Submitter: Connie Wang

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

Version: 1

Publication Details
Horng JC;Demarest SJ;Raleigh DP,Proteins (2003) pH-dependent stability of the human alpha-lactalbumin molten globule state: contrasting roles of the 6 - 120 disulfide and the beta-subdomain at low and neutral pH. PMID:12833543
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
1CB3 1999-06-08 LOCAL INTERACTIONS DRIVE THE FORMATION OF NON-NATIVE STRUCTURE IN THE DENATURED STATE OF HUMAN ALPHA-LACTALBUMIN: A HIGH RESOLUTION STRUCTURAL CHARACTERIZATION OF A PEPTIDE MODEL IN AQUEOUS SOLUTION
1B9O 1999-03-31 1.15 HUMAN ALPHA-LACTALBUMIN, LOW TEMPERATURE FORM
3B0O 2012-06-13 1.61 Crystal structure of alpha-lactalbumin
1HML 1995-01-26 1.7 ALPHA_LACTALBUMIN POSSESSES A DISTINCT ZINC BINDING SITE
1ALC 1989-10-15 1.7 REFINED STRUCTURE OF BABOON ALPHA-LACTALBUMIN AT 1.7 ANGSTROMS RESOLUTION. COMPARISON WITH C-TYPE LYSOZYME
3B0I 2012-06-13 1.8 Crystal structure of recombinant human alpha lactalbumin
1A4V 1999-04-27 1.8 ALPHA-LACTALBUMIN
4L41 2013-10-02 2.7 Human Lactose synthase: A 2:1 complex between human alpha-lactalbumin and human beta1,4-galactosyltransferase

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
91.7 Alpha-lactalbumin P37154 LALBA_FELCA
94.3 Alpha-lactalbumin P12065 LALBA_PAPCY
100.0 Alpha-lactalbumin P00709 LALBA_HUMAN