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Surface salt bridges stabilize the GCN4 leucine zipper
Author(s) -
Spek Erik J.,
Bui Au H.,
Lu Min,
Kallenbach Neville R.
Publication year - 1998
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560071121
Subject(s) - leucine zipper , zipper , chemistry , bzip domain , basic helix loop helix leucine zipper transcription factors , biophysics , microbiology and biotechnology , crystallography , biochemistry , biology , transcription factor , dna binding protein , computer science , gene , algorithm
We present a study of the role of salt bridges in stabilizing a simplified tertiary structural motif, the coiled‐coil. Changes in GCN4 sequence have been engineered that introduce trial patterns of single and multiple salt bridges at solvent exposed sites. At the same sites, a set of alanine mutants was generated to provide a reference for thermodynamic analysis of the salt bridges. Introduction of three alanines stabilizes the dimer by 1. 1 kcal/mol relative to the wild‐type. An arrangement corresponding to a complex type of salt bridge involving three groups stabilizes the dimer by 1. 7 kcal/mol, an apparent elevation of the melting temperature relative to wild type of about 22°C. While identifying local from nonlocal contributions to protein stability is difficult, stabilizing interactions can be identified by use of cycles. Introduction of alanines for side chains of lower helix propensity and complex salt bridges both stabilize the coiled‐coil, so that combining the two should yield melting temperatures substantially higher than the starting species, approaching those of thermophilic sequences.