Hostname: page-component-78c5997874-lj6df Total loading time: 0 Render date: 2024-11-11T03:15:23.181Z Has data issue: false hasContentIssue false

Thermodynamic and structural characterization of Asn and Ala residues in the disallowed II′ region of the Ramachandran plot

Published online by Cambridge University Press:  10 February 2001

M. CRISTINA VEGA
Affiliation:
EMBL, Meyerhofstrasse 1, 69117 Heidelberg, Germany
JOSE C. MARTÍNEZ
Affiliation:
Departamento de Química Física, Facultad de Ciencias, Universidad de Granada, 18071-Granada, Spain
LUIS SERRANO
Affiliation:
EMBL, Meyerhofstrasse 1, 69117 Heidelberg, Germany
Get access

Abstract

Residue Asn47 at position L1 of a type II′ β-turn of the α-spectrin SH3 domain is located in a disallowed region of the Ramachandran plot (φ = 56 ± 12, ψ = −118 ± 17). Therefore, it is expected that replacement of Asn47 by Gly should result in a considerable stabilization of the protein. Thermodynamic analysis of the N47G and N47A mutants shows that the change in free energy is small (∼0.7 kcal/mol; ∼3 kJ/mol) and comparable to that found when mutating a Gly to Ala in a α-helix or β-sheet. X-ray structural analysis of these mutants shows that the conformation of the β-turn does not change upon mutation and, therefore, that there is no relaxation of the structure, nor is there any gain or loss of interactions that could explain the small energy change. Our results indicate that the energetic definition of II′ region of the Ramachandran plot (φ = 60 ± 30, ψ = −115 ± 15) should be revised for at least Ala and Asn in structure validation and protein design.

Type
Research Article
Copyright
© 2000 The Protein Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)