His-tag impact on structure.
Crystallographers are increasingly determining structures of protein constructs that include His tags. Many have taken for granted that these tags have little effect on the native structure. This paper surveys and compares crystal structures with and without His tags. It is observed that actual refined tag residues fitted into density occur in less that 10% of the tagged sequences. However, higher resolution crystals are observed when this occurs. It is shown that these purification tags generally have no significant effect on the structure of the native protein. Resolution and R factors are not affected, but the overall B factors are slightly higher. Additional annotation in the PDB format to make tag definition explicit is suggested.
Carson
Mike
M
Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham, 251 CBSE, 1025 18th Street South, Birmingham, AL 35294-4400, USA. carson@uab.edu
Johnson
David H
DH
McDonald
Heather
H
Brouillette
Christie
C
Delucas
Lawrence J
LJ
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D030562:Databases, Protein / Q000592:standards*; D006639:Histidine / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D012107:Research Design / Q000592:standards* / Q000706:statistics & numerical data
D011506:Proteins; D006639:Histidine