Open AccessStructural Analysis of the Effect of a Dual-FLAG Tag on Transthyretin
Author(s) -
Mehdi Shirzadeh,
Michael L. Poltash,
Arthur Laganowsky,
David H. Russell
Publication year - 2020
Publication title -
biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.43
H-Index - 253
eISSN - 1520-4995
pISSN - 0006-2960
DOI - 10.1021/acs.biochem.0c00105
Subject(s) - chemistry , transthyretin , flag tag , recombinant dna , electrospray ionization , fragmentation (computing) , cleavage (geology) , biophysics , mass spectrometry , biochemistry , fusion protein , chromatography , biology , ecology , paleontology , endocrinology , fracture (geology) , gene
Recombinant proteins have increased our knowledge regarding the physiological role of proteins; however, affinity purification tags are often not cleaved prior to analysis, and their effects on protein structure, stability and assembly are often overlooked. In this study, the stabilizing effects of an N-terminus dual-FLAG (FT 2 ) tag fusion to transthyretin (TTR), a construct used in previous studies, are investigated using native ion mobility-mass spectrometry (IM-MS). A combination of collision-induced unfolding and variable-temperature electrospray ionization is used to compare gas- and solution-phase stabilities of FT 2 -TTR to wild-type and C-terminal tagged TTR. Despite an increased stability of both gas- and solution-phase FT 2 -TTR, thermal degradation of FT 2 -TTR was observed at elevated temperatures, viz., backbone cleavage occurring between Lys9 and Cys10. This cleavage reaction is consistent with previously reported metalloprotease activity of TTR [Liz et al. 2009] and is suppressed by either metal chelation or excess zinc. This study brings to the fore the effect of affinity tag stabilization of TTR and emphasizes unprecedented detail afforded by native IM-MS to assess structural discrepancies of recombinant proteins from their wild-type counterparts.