Solution NMR structures of IgG binding domains with artificially evolved high levels of sequence identity but different folds.

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TitleSolution NMR structures of IgG binding domains with artificially evolved high levels of sequence identity but different folds.
Publication TypeJournal Article
Year of Publication2005
AuthorsHe, Y, Yeh, DCheon, Alexander, P, Bryan, PN, Orban, J
JournalBiochemistry
Volume44
Issue43
Pagination14055-61
Date Published2005 Nov 1
ISSN0006-2960
KeywordsAmino Acid Sequence, Binding Sites, Crystallography, X-Ray, Immunoglobulin G, Magnetic Resonance Spectroscopy, Molecular Sequence Data, Mutation, Nerve Tissue Proteins, Protein Folding, Protein Structure, Secondary, Staphylococcal Protein A, Thermodynamics
Abstract

We describe here the solution NMR structures of two IgG binding domains with highly homologous sequences but different three-dimensional structures. The proteins, G311 and A219, are derived from the IgG binding domains of their wild-type counterparts, protein G and protein A, respectively. Through a series of site-directed mutations and phage display selections, the sequences of G311 and A219 were designed to converge to a point of high-level sequence identity while keeping their respective wild-type tertiary folds. Structures of both artificially evolved sequences were determined by NMR spectroscopy. The main chain fold of G311 can be superimposed on the wild-type alpha/beta protein G structure with a backbone rmsd of 1.4 A, and the A219 structure can be overlaid on the wild-type three-alpha-helix protein A fold also with a backbone rmsd of 1.4 A. The structure of G311, in particular, accommodates a large number of mutational changes without undergoing a change in the overall fold of the main chain. The structural differences are maintained despite a high level (59%) of sequence identity. These proteins serve as starting points for further experiments that will probe basic concepts of protein folding and conformational switching.

DOI10.1021/bi051232j
Alternate JournalBiochemistry
PubMed ID16245921
Grant ListGM62154 / GM / NIGMS NIH HHS / United States