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Methods for the Purification of HQ-Tagged Proteins
Becky Godat, Laurie Engel, Natalie A. Betz, and Tonny M. Johnson
Summary
The HQ (H = histidine, Q = glutamine) tag is a small fusion tag that can be isolated
using immobilized metal affinity columns. HQ-tagged proteins can be expressed and
purified from bacterial cells under native and denaturing conditions, mammalian cells,
insect cells, wheat germ and rabbit reticulocyte. Furthermore, HQ-tagged proteins can be
purified using magnetic or non-magnetic resins in multiple formats from small to largescale
and manual or automated. In this chapter, we have described various protocols for
the purification of HQ-tagged proteins.
Key Words: Protein expression; HQ-tagged proteins; recombinant protein; magnetic
resin; non-magnetic resin; protein purification; automated protein purification; highthroughput
protein purification.
1. Introduction
Protein fusion tags are essential tools for the isolation and purification of
proteins for the study of protein–protein and protein–ligand interactions; and
protein structure-function studies (1–6). Many fusion tags are available for the
expression and purification of recombinant proteins using immobilized affinity
metal chromatography (IMAC) (7–8). Among these, the polyhistidine tag is
most commonly used for several reasons including that the tag is very small,
can be used under native or denaturing conditions and is not immunogenic.
The HQ tag is a metal affinity tag consisting of 6–10 amino acids (repeating
HQs; H = histidine, Q = glutamine) and is similar in function to polyhistidine
From: Methods in Molecular Biology, vol. 421: Affinity Chromatography: Methods and Protocols, Second Edition
Edited by: M. Zachariou © Humana Press, Totowa, NJ
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