FIGURE 1. Structure and nucleotide binding-properties of 
-tubulin.
From the following article:
Insights into microtubule nucleation from the crystal structure of human 
-tubulin
Hector Aldaz, Luke M. Rice, Tim Stearns and David A. Agard
Nature 435, 523-527 (26 May 2005)
doi: 10.1038/nature03586
a, Cartoon representation of the -tubulin structure. b, Representative electron density from a complete annealed 
A-weighted 2mFo - DFc map computed from the final model. GTP-S and interacting residues are shown. c, Nucleotide binding studies reveal that -tubulin (left) and the exchangeable site on 
-tubulin (right) have similar GTP/GDP binding properties. The affinities of -tubulin and -tubulin for GTP are 58.4 
12.6 nM and 64.5 6.3 nM (respectively) and GDP affinities are 1.13 0.2 µM for -tubulin and 1.55 0.25 µM for -tubulin.