Purification of Shiga-like toxin 1 by pigeon egg white glycoproteins immobilized on Sepharose gels

The galabiose structure Galα1-4Gal is rarely found in natural glycoproteins, but is abundantly present in pigeon egg white proteins as Galα(1-4)Galβ(1-4)GlcNAc termini. Pigeon ovalbumin, ovomucoid, or the whole egg white were immobilized on periodate-oxidized Sepharose CL-6B gels by reductive amination. These gels were found to bind Shiga-like toxin type 1 (SLT-1) specifically and efficiently. SLT-1 was eluted from the gel beads with 0.5 M melibiose, which was more efficient and milder than elution with 4.5 M MgCl₂. SLT-1 was purified to homogeneity from the crude extract of Escherichia coli SLT100 expressing SLT-1 by a single affinity chromatographic step in 83-88% yield. The capacity of the gel was estimated to be ca. 1 mg toxin/ml gel. Interestingly, SLT-2 was not bound by these affinity gels containing Galα1-4Galβ1-4GlcNAc termini. Since SLT-2 has been shown to bind to Galα1-4Galβ1-4Glc-terminating compounds, our results suggest that Glc in globotriose moiety is important for binding SLT-2, and replacing the Glc with GlcNAc in this triose renders it ineffective for binding SLT-2.