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Engineering the cytokinin-glucoside specificity of the maize beta-D-glucosidase Zm-p60.1 using site-directed random mutagenesis

Basic information
Original title:Engineering the cytokinin-glucoside specificity of the maize beta-D-glucosidase Zm-p60.1 using site-directed random mutagenesis
Authors:Tomáš Filipi, Pavel Mazura, Lubomír Janda, Nagavalli Subbanna Kiran, Břetislav Brzobohatý
Further information
Citation:FILIPI, Tomáš, Pavel MAZURA, Lubomír JANDA, Nagavalli Subbanna KIRAN and Břetislav BRZOBOHATÝ. Engineering the cytokinin-glucoside specificity of the maize beta-D-glucosidase Zm-p60.1 using site-directed random mutagenesis. Phytochemistry, Oxford, UK: Elsevier Science, 2012, vol. 74, p. 40-48. ISSN 0031-9422. doi:10.1016/j.phytochem.2011.10.008.Export BibTeX
@article{968261,
author = {Filipi, Tomáš and Mazura, Pavel and Janda, Lubomír and Kiran, Nagavalli Subbanna and Brzobohatý, Břetislav},
article_location = {Oxford, UK},
doi = {http://dx.doi.org/10.1016/j.phytochem.2011.10.008},
keywords = {(alpha/beta)(8) Barrel; beta-Glucosidase; cis-Zeatin-O-beta-D-glucopyranoside; Cytokinin metabolism; Glycosidase; Protein engineering; Site-directed random mutagenesis; Substrate specificity; trans-Zeatin-O-beta-D-glucopyranoside; trans-Zeatin-9-beta-D-glucopyranoside},
language = {eng},
issn = {0031-9422},
journal = {Phytochemistry},
title = {Engineering the cytokinin-glucoside specificity of the maize beta-D-glucosidase Zm-p60.1 using site-directed random mutagenesis},
volume = {74},
year = {2012}
}
Original language:English
Field:Biochemistry
Type:Article in Periodical
Keywords:(alpha/beta)(8) Barrel; beta-Glucosidase; cis-Zeatin-O-beta-D-glucopyranoside; Cytokinin metabolism; Glycosidase; Protein engineering; Site-directed random mutagenesis; Substrate specificity; trans-Zeatin-O-beta-D-glucopyranoside; trans-Zeatin-9-beta-D-glucopyranoside

The maize beta-D-glucosidase Zm-p60.1 releases active cytokinins from their storage/transport forms, and its over-expression in tobacco disrupts zeatin metabolism. The role of the active-site microenvironment in fine-tuning Zm-p60.1 substrate specificity has been explored, particularly in the W373K mutant, using site-directed random mutagenesis to investigate the influence of amino acid changes around the 373 position. Two triple (P372T/W373K/M376L and P372S/W373K/M376L) and three double mutants (P372T/W373K, P372S/W373K and W373K/M376L) were prepared. Their catalytic parameters with two artificial substrates show tight interdependence between substrate catalysis and protein structure. P372T/W373K/M376L exhibited the most significant effect on natural substrate specificity: the ratio of hydrolysis of cis-zeatin-O-beta-D-glucopyranoside versus the trans-zeatin-O-beta-D-glucopyranoside shifted from 1.3 in wild-type to 9.4 in favor of the cis- isomer. The P372T and M376L mutations in P372T/W373K/M376L also significantly restored the hydrolytic velocity of the W373K mutant, up to 60% of wild-type velocity with cis-zeatin-O-beta-D-glucopyranoside. These findings reveal complex relationships among amino acid residues that modulate substrate specificity and show the utility of site-directed random mutagenesis for changing and/or fine-tuning enzymes. Preferential cleavage of specific isomer-conjugates and the capacity to manipulate such preferences will allow the development of powerful tools for detailed probing and fine-tuning of cytokinin metabolism in planta. (C) 2011 Elsevier Ltd. All rights reserved.

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