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Dissection of the protein G B1 domain binding site for human IgG Fc fragment
Author(s) -
Sloan David J.,
Hellinga Homme W.
Publication year - 1999
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 - 10.1110/ps.8.8.1643
Subject(s) - alanine scanning , alanine , chemistry , polar , mutagenesis , crystallography , binding site , hydrogen bond , biophysics , fragment crystallizable region , plasma protein binding , immunoglobulin fc fragments , protein structure , residue (chemistry) , protein–protein interaction , stereochemistry , mutation , immunoglobulin g , molecule , biochemistry , antibody , receptor , amino acid , biology , genetics , physics , gene , organic chemistry , astronomy
Abstract The contribution to the free energy of binding of each of the residues forming the binding site for a human IgG Fc fragment on the surface of the B1 domain of protein G was determined by alanine‐scanning mutagenesis. The interface between these two proteins is atypical in that it is smaller than usual, polar in character, and involves two well‐defined “knobs‐into‐holes” interactions. The bulk of the free energy of binding is contributed by three central residues, which make hydrogen bonds across the interface. Of these, the most critical interaction is formed by Glu27, which acts as a charged knob on the surface of the B1 domain, inserting into a polar hole on the Fc fragment. A single alanine mutation of this residue virtually abolishes stable complex formation. Formation of a stable interface between these two proteins is therefore dominated by a small, polar “hot spot.”