RESUMO
The development of a stable L-BDH chimera was attempted by exchanging whole domains between two native structural analogs, L-BDH and meso-BDH, because the S-configuration specificity of L-BDH is valuable from the standpoint of its application but its activity is unstable, whereas meso-BDH is stable. The domain chimeras obtained indicated that the leaf-like structures constituting three domains were likely to be mainly associated with chiral recognition, and the fourth domain, the basic domain, is likely to be mainly associated with enzyme stability. A combination of the leaf domains of L-BDH and the basic domain of meso-BDH attained a sufficient level of practical use as an artificial L-BDH chimera, because the resulting enzyme had both stability and S-configuration specificity. However, the levels of stability and specificity were slightly lower than those of the respective enzymes from which they were derived.
Assuntos
Oxirredutases do Álcool/química , Oxirredutases do Álcool/genética , Oxirredutases do Álcool/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Estabilidade Enzimática , Escherichia coli/genética , Escherichia coli/metabolismo , Cinética , Modelos Moleculares , Anotação de Sequência Molecular , Dados de Sequência Molecular , Engenharia de Proteínas , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Alinhamento de Sequência , Estereoisomerismo , Especificidade por SubstratoRESUMO
2,3-butanediol dehydrogenase (BDH) catalyzes the NAD-dependent redox reaction between acetoin and 2,3-butanediol. There are three types of homologous BDH, each stereospecific for both substrate and product. To establish how these homologous enzymes possess differential stereospecificities, we determined the crystal structure of l-BDH with a bound inhibitor at 2.0 A. Comparison with the inhibitor binding mode of meso-BDH highlights the role of a hydrogen-bond from a conserved Trp residue(192). Site-directed mutagenesis of three active site residues of meso-BDH, including Trp(190), which corresponds to Trp(192) of L-BDH, converted its stereospecificity to that of L-BDH. This result confirms the importance of conserved residues in modifying the stereospecificity of homologous enzymes.