Structure and dimerization of translation initiation factor aIF5B in solution

► aIF5B forms maximum 5.0-6.8% irreversible dimers in solution. ► Sedimentation coefficients for monomer and dimer are 3.64 and 5.51 ± 0.29 S. ► Adding only 2% glycerol prevents dimerization. ► SAXS on aIF5B monomer gave an Rg of 37.5 ± 0.2 Å and a Dmax of ∼130 Å. ► There are universal structural differences between aIF5B and Escherichia coli IF2.