Cloning and characterization of a gene encoding ABP57, a soluble auxin-binding protein

Abstract

Auxin-binding protein 57 (ABP57), a soluble auxin-binding protein, acts as a receptor to activate plasma membrane (PM) H+-ATPase. Here, we report the cloning of abp57 and the biochemical characterization of its protein expressed in E. coli. The analysis of internal amino acid sequences of ABP57 purified from rice shoots enabled us to search for the corresponding gene in protein DB of NCBI. Further BLAST analysis showed that rice has four abp57-like genes and maize has at least one homolog. Interestingly, Arabidopsis seems to have no homolog. Recombinant ABP57 expressed in E. coli caused the activation of PM H+-ATPase regardless of the existence of IAA. Scatchard analysis showed that the recombinant protein has relatively low affinity to IAA as compared to natural ABP57. These results collectively support the notion that the cloned gene is responsible for ABP57.