[beta]-AMYLASE4, a Noncatalytic Protein Required for Starch Breakdown, Acts Upstream of Three Active [beta]-Amylases in Arabidopsis Chloroplasts(W)(OA)

From: Plant Cell | Date: April 1, 2008| Author: | Copyright information

This work investigated the roles of β-amylases in the breakdown of leaf starch. Of the nine β-amylase (BAM)-like proteins encoded in the Arabidopsis thaliana genome, at least four (BAM1, -2, -3, and -4) are chloroplastic. When expressed as recombinant proteins in Escherichia coli, BAM1, BAM2, and BAM3 had measurable β-amylase activity but BAM4 did not. BAM4 has multiple amino acid substitutions relative to characterized β-amylases, including one of the two catalytic residues. Modeling predicts major differences between the glucan binding site of BAM4 and those of active ...

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