Affinity tags can reduce merohedral twinning of membrane protein crystals.
This work presents a comparison of the crystal packing of three eukaryotic membrane proteins: human aquaporin 1, human aquaporin 5 and a spinach plasma membrane aquaporin. All were purified from expression constructs both with and without affinity tags. With the exception of tagged aquaporin 1, all constructs yielded crystals. Two significant effects of the affinity tags were observed: crystals containing a tag typically diffracted to lower resolution than those from constructs encoding the protein sequence alone and constructs without a tag frequently produced crystals that suffered from merohedral twinning. Twinning is a challenging crystallographic problem that can seriously hinder solution of the structure. Thus, for integral membrane proteins, the addition of an affinity tag may help to disrupt the approximate symmetry of the protein and thereby reduce or avoid merohedral twinning.
Backmark
Anna
A
Department of Chemical and Biological Engineering, Chalmers University of Technology, PO Box 462, SE-40530 Gothenburg, Sweden.
Nyblom
Maria
M
Törnroth-Horsefield
Susanna
S
Kosinska-Eriksson
Urszula
U
Nordén
Kristina
K
Fellert
Maria
M
Kjellbom
Per
P
Johanson
Urban
U
Hedfalk
Kristina
K
Lindkvist-Petersson
Karin
K
Neutze
Richard
R
Horsefield
Rob
R
D000345:Affinity Labels / Q000737:chemistry* / Q000378:metabolism; D020346:Aquaporins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D006801:Humans; D010843:Pichia; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018724:Spinacia oleracea
D000345:Affinity Labels; D020346:Aquaporins; D010940:Plant Proteins; D011994:Recombinant Proteins