Mutants of common bean alpha-amylase inhibitor-2 as an approach to investigate binding specificity to alpha-amylases

Pesquisa Agropecuária Brasileira

Maria Cristina Mattar Da Silva²  Luciane Vieira Mello²  Marise Ventura Coutinho²  Daniel John Rigden²  Goran Neshich¹  Maarten John Chrispeels¹  Maria Fátima Grossi-de-sá² 

[1] ,Embrapa Recursos Genéticos e Biotecnologia Parque Estação Biológica Brasília DF ,Brazil

关键词: Phaseolus vulgaris;    a-amylase inhibitors;    inhibitor specificity;    site directed mutagenesis;    structural modeling;    Phaseolus vulgaris;    inibidores de a-amilases;    especificidade de interação;    mutagênese sítio-dirigida;    modelagem molecular;   

DOI  :  10.1590/S0100-204X2004000300001

来源: SciELO

【 摘 要 】

Despite the presence of a family of defense proteins, Phaseolus vulgaris can be attacked by bruchid insects resulting in serious damage to stored grains. The two distinct active forms of a-amylase inhibitors, a-AI1 and a-AI2, in P. vulgaris show different specificity toward a-amylases. Zabrotes subfasciatus a-amylase is inhibited by a-AI2 but not by a-AI1. In contrast, porcine a-amylase is inhibited by a-AI1 but not by a-AI2. The objective of this work was to understand the molecular basis of the specificity of two inhibitors in P. vulgaris (a-AI1 and a-AI2) in relation to a-amylases. Mutants of a-AI2 were made and expressed in tobacco plants. The results showed that all the a-AI2 mutant inhibitors lost their activity against the insect a-amylases but none exhibited activity toward the mammalian a-amylase. The replacement of His33 of a-AI2 with the a-AI1-like sequence Ser-Tyr-Asn abolished inhibition of Z. subfasciatus a-amylase. From structural modeling, the conclusion is that the size and complexity of the amylase-inhibitor interface explain why mutation of the N-terminal loop and resultant abolition of Z. subfasciatus a-amylase inhibition are not accompanied by gain of inhibitory activity against porcine a-amylase.

【 授权许可】

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