Context is a major determinant of beta-sheet propensity.
Residues in beta-sheets occur in two distinct tertiary contexts: central strands, bordered on both sides by other beta-strands, and edge strands, bordered on only a single side by another beta-strand. The delta delta G values for beta-sheet formation measured at an edge beta-strand of the IgG-binding domain of protein G(GB1) are quite different from those obtained previously at a central position in the same protein. In particular, there is no correlation at the edge position with statistically determined beta-sheet-forming preferences. The differences between beta-sheet propensities measured at central and edge beta-strands, delta delta delta G values, correlate with the values of water/octanol transfer free energies and side-chain non-polar surface area for the amino acids. These results strongly suggest that, unlike alpha-helix formation, beta-sheet formation is determined in large part by tertiary context, even at solvent-accessible sites, and not by intrinsic secondary structure preferences.
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Department of Chemistry, Howard Hughes Medical Institute, Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge 02142.
Kim
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D000409:Alanine / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D004735:Energy Transfer; D004926:Escherichia coli; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins
D000596:Amino Acids; D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus; D007141:Immunoglobulin Fc Fragments; D011994:Recombinant Proteins; D000409:Alanine