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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Curr Opin Struct Biol. 2010 Aug 11;20(5):536–542. doi: 10.1016/j.sbi.2010.07.004

Figure 4.

Figure 4

In the lactose synthase complex (left), α-LA modulates the sugar acceptor specificity of the β4Gal-T1 enzyme from GlcNAc to Glc, while in the αpptGalNAc-Ts (right), although the catalytic domain alone exhibits catalytic activity, the lectin domain defines acceptor substrate specificity to the enzyme. Thus, in these proteins α-LA and the lectin domain are considered as “add-on” domains. There are many other transferases found where such a domain brings about substrate specificity to the enzyme.