Anion-induced stabilization of human serum albumin prevents the formation of intermediate during urea denaturation.


Abstract

The unfolding of human serum albumin (HSA), a multidomain protein, by urea was followed by far-UV circular dichroism (CD), intrinsic fluorescence, and ANS fluorescence measurements. The urea-induced transition, which otherwise was a two-step process with a stable intermediate at around 4.8 M urea concentration as monitored by far-UV CD and intrinsic fluorescence, underwent a single-step cooperative transition in the presence of 1.0 M KCl. The free energy of stabilization (DeltaDelta G(H2O)D) in the presence of 1 M KCl was found to be 1,090 and 1,200 cal/mol as determined by CD and fluorescence, respectively. The salt stabilization occurred in the first transition (0-5.0 M urea), which corresponded to the formation of intermediate (I) state from the native (N) state, whereas the second transition, corresponding to the unfolding of I state to denatured (D) state, remained unaffected. Urea denaturation of HSA as monitored by tryptophan fluorescence of the lone tryptophan residue (Trp(214)) residing in domain II of the protein, followed a single-step transition suggesting that domain(s) I and/or III is (are) involved in the intermediate formation. This was also confirmed by the acrylamide quenching of tryptophan fluorescence at 5 M urea, which exhibited little change in the value of Stern-Volmer constant. ANS fluorescence data also showed single-step transition reflecting the absence of accumulation of hydrophobic patches. The stabilizing potential of various salts studied by far-UV CD and intrinsic fluorescence was found to follow the order: NaClO(4) > NaSCN >Na(2)SO(4) >KBr >KCl >KF. A comparison of the effects of various potassium salts revealed that anions were chiefly responsible in stabilizing HSA. The above series was found similar to the electroselectivity series of anions towards the anion-exchange resins and reverse of the Hofmeister series, suggesting that preferential binding of anions to HSA rather than hydration, was primarily responsible for stabilization. Further, single-step transition observed with GdnHCl can be ascribed to its ionic character as the free energy change associated with urea denaturation in the presence of 1.0 M KCl (5,980 cal/mol) was similar to that obtained with GdnHCl (5,870 cal/mol). Study holds ProTherm entries: 8043, 8044, 8045, 8046 Extra Details: the transition is from native to intermediate N->I

Submission Details

ID: rGJS6RsX4

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:35 p.m.

Version: 1

Publication Details
Muzammil S;Kumar Y;Tayyab S,Proteins (2000) Anion-induced stabilization of human serum albumin prevents the formation of intermediate during urea denaturation. PMID:10813828
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
1AO6 1997-07-18T00:00:00+0000 2.5 CRYSTAL STRUCTURE OF HUMAN SERUM ALBUMIN
1BJ5 1998-07-02T00:00:00+0000 2.5 HUMAN SERUM ALBUMIN COMPLEXED WITH MYRISTIC ACID
1BKE 1998-07-06T00:00:00+0000 3.15 HUMAN SERUM ALBUMIN IN A COMPLEX WITH MYRISTIC ACID AND TRI-IODOBENZOIC ACID
1BM0 1998-07-28T00:00:00+0000 2.5 CRYSTAL STRUCTURE OF HUMAN SERUM ALBUMIN
1E78 2000-08-25T00:00:00+0000 2.6 Crystal structure of human serum albumin
1E7A 2000-08-26T00:00:00+0000 2.2 Crystal structure of human serum albumin complexed with the general anesthetic propofol
1E7B 2000-08-26T00:00:00+0000 2.38 Crystal structure of human serum albumin complexed with the general anesthetic halothane
1E7C 2000-08-26T00:00:00+0000 2.4 HUMAN SERUM ALBUMIN COMPLEXED WITH MYRISTIC ACID and the general anesthetic halothane
1E7E 2000-08-29T00:00:00+0000 2.5 HUMAN SERUM ALBUMIN COMPLEXED WITH DECANOIC ACID (CAPRIC ACID)
1E7F 2000-08-29T00:00:00+0000 2.43 HUMAN SERUM ALBUMIN COMPLEXED WITH DODECANOIC ACID (LAURIC ACID)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 SERUM ALBUMIN P02768 ALBU_HUMAN
98.5 SERUM ALBUMIN Q5NVH5 ALBU_PONAB
93.7 Serum albumin A2V9Z4 ALBU_MACFA
93.7 Serum albumin Q28522 ALBU_MACMU