Thermodynamics of the helix-coil transition: Binding of S15 and a hybrid sequence, disulfide stabilized peptide to the S-protein

• Type: Article in International Scientific Journal
• Date: 2001

Authors

Bastos, M (Author) FCUP; Pease, JHB (Author) Other; Wemmer, DE (Author) Other; Murphy, KP (Author) Other; Connelly, PR (Author) Other

Journal

Title: Proteins: Structure, Function and Genetics

Vol. 42

Pages: 523-530

ISSN: 0887-3585

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 10 Citations

Scopus - 9 Citations

Scientific classification

FOS: Natural sciences > Biological sciences

Other information

Authenticus ID: P-000-WB0

DOI: 10.1002/1097-0134(20010301)42:4<523::aid-prot100>3.0.co;2-b

Abstract (EN): Pancreatic ribonuclease A may be cleaved to produce two fragments: the S-peptide (residues 1-20) and the S-protein (residues 21-124), The S-peptide, or a truncated version designated as the S15 peptide (residues 1-15), combines with the S-protein to produce catalytically active complexes. The conformation of these peptides and many of their analogues is predominantly random coil at room temperature; however, they populate a significant fraction of helical form at low temperature under certain solution conditions. Moreover, they adopt a helical conformation when bound to the S-protein. A hybrid sequence, disulfide-stabilized peptide (ApaS-25), designed to stabilize the helical structure of the S-peptide in solution, also combines with the S-protein to yield a catalytically active complex. We have performed high-precision titration microcalorimetric measurements to determine the free energy, enthalpy, entropy, and heat capacity changes for the binding of ApaS-25 to S-protein within the temperature range 5-25 degreesC. The thermodynamic parameters for both the complex formation reactions and the helix-to-coil transition also were calculated, using a structure-based approach, by calculating changes in accessible surface area and using published empirical parameters. A simple thermodynamic model is presented in an attempt to account for the differences between the binding of ApaS-25 and the S-peptide, From this model, the thermodynamic parameters of the helix-to-coil transition of S15 can be calculated. (C) 2001 Wiley-Liss, Inc.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8