A minimal sequence code for switching protein structure and function.

Printer-friendly versionPrinter-friendly versionPDF versionPDF version
TitleA minimal sequence code for switching protein structure and function.
Publication TypeJournal Article
Year of Publication2009
AuthorsAlexander, PA, He, Y, Chen, Y, Orban, J, Bryan, PN
JournalProc Natl Acad Sci U S A
Volume106
Issue50
Pagination21149-54
Date Published2009 Dec 15
ISSN1091-6490
KeywordsHumans, Immunoglobulin G, Magnetic Resonance Spectroscopy, Mutagenesis, Site-Directed, Mutation, Protein Conformation, Protein Engineering, Protein Folding, Protein Stability, Recombinant Fusion Proteins, Serum Albumin, Subtilisin
Abstract

We present here a structural and mechanistic description of how a protein changes its fold and function, mutation by mutation. Our approach was to create 2 proteins that (i) are stably folded into 2 different folds, (ii) have 2 different functions, and (iii) are very similar in sequence. In this simplified sequence space we explore the mutational path from one fold to another. We show that an IgG-binding, 4beta+alpha fold can be transformed into an albumin-binding, 3-alpha fold via a mutational pathway in which neither function nor native structure is completely lost. The stabilities of all mutants along the pathway are evaluated, key high-resolution structures are determined by NMR, and an explanation of the switching mechanism is provided. We show that the conformational switch from 4beta+alpha to 3-alpha structure can occur via a single amino acid substitution. On one side of the switch point, the 4beta+alpha fold is >90% populated (pH 7.2, 20 degrees C). A single mutation switches the conformation to the 3-alpha fold, which is >90% populated (pH 7.2, 20 degrees C). We further show that a bifunctional protein exists at the switch point with affinity for both IgG and albumin.

DOI10.1073/pnas.0906408106
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID19923431
PubMed Central IDPMC2779201
Grant ListGM62154 / GM / NIGMS NIH HHS / United States