Semi-synthesis of an artificial scandium(III) enzyme with a β-helical bio-nanotube.
We have succeeded in preparing semi-synthesized proteins bound to Sc(3+) ion which can promote an epoxide ring-opening reaction. The Sc(3+) binding site was created on the surface of [(gp5βf)(3)](2) (N. Yokoi et al., Small, 2010, 6, 1873) by introducing a cysteine residue for conjugation of a bpy moiety using a thiol-maleimide coupling reaction. Three cysteine mutants [(gp5βf_X)(3)](2) (X = G18C, L47C, N51C) were prepared to introduce a bpy in different positions because it had been reported that Sc(3+) ion can serve as a Lewis-acid catalyst for an epoxide ring-opening reaction upon binding of epoxide to bpy and two -ROH groups. G18C_bpy with Sc(3+) can accelerate the rate of catalysis of the epoxide ring-opening reaction and has the highest rate of conversion among the three mutants. The value is more than 20 times higher than that of the mixtures of [(gp5βf)(3)](2)/2,2'-bipyridine and L-threonine/2,2'-bipyridine. The elevated activity was obtained by the cooperative effect of stabilizing the Sc(3+) coordination and accumulation of substrates on the protein surface. Thus, we expect that the semi-synthetic approach can provide insights into new rational design of artificial metalloenzymes.
Graduate School of Engineering, Kyoto Univ., Katsura, Kyoto 615-8510, Japan.
Hiroshi
H
Inaba
Shuji
S
Kanamaru
Fumio
F
Arisaka
Susumu
S
Kitagawa
Takafumi
T
Ueno
D020816:Amino Acid Motifs; D001665:Binding Sites; D056246:Chemistry, Analytic; D004798:Enzymes / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry*; D012538:Scandium / Q000737:chemistry
D004798:Enzymes; D012538:Scandium