Comparison of the structures and the crystal contacts of trypanosomal triosephosphate isomerase in four different crystal forms.
Triosephosphate isomerase (TIM) is a dimeric enzyme consisting of 2 identical subunits. Trypanosomal TIM can be crystallized in 4 different spacegroups: P2(1)2(1)2(1), C2(big cell), C2(small cell), and P1. The P1 crystal form only grows in the presence of 1.4 M DMSO; there are 2 DMSO binding sites per subunit. The structures have been refined at a resolution of 1.83 A, 2.10 A, 2.13 A, and 1.80 A, respectively. In the 4 different spacegroups the TIM subunit can be observed in the context of 7 different crystallographic environments. In the C2 cells, the dimer 2-fold axis coincides with a crystallographic 2-fold axis. The similarities and differences of the 7 subunits are discussed. In 6 subunits the flexible loop (loop 6) is open, whereas in the P2(1)2(1)2(1) cell, the flexible loop of subunit 2 is in an almost closed conformation. The crystal contacts in the 4 different crystal forms are predominantly generated by polar residues in loops. A statistical analysis of the residues involved in crystal contacts shows that, in particular, serines are frequently involved in these interactions; 19% of the exposed serines are involved in crystal contacts.
Kishan
K V
KV
European Molecular Biology Laboratory, Heidelberg, Germany.
Zeelen
J P
JP
Noble
M E
ME
Borchert
T V
TV
Wierenga
R K
RK
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D004121:Dimethyl Sulfoxide; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011487:Protein Conformation; D014305:Triose-Phosphate Isomerase / Q000737:chemistry* / Q000235:genetics; D014345:Trypanosoma / Q000201:enzymology
D014305:Triose-Phosphate Isomerase; D004121:Dimethyl Sulfoxide