4MLA

Structure of maize cytokinin oxidase/dehydrogenase 2 (ZmCKO2)

Summary for 4MLA

• Entry DOI: 10.2210/pdb4mla/pdb
• Related: 3S1D 4ML8
• Descriptor: Cytokinin oxidase 2, FLAVIN-ADENINE DINUCLEOTIDE, ISOPROPYL ALCOHOL, ... (6 entities in total)
• Functional Keywords: oxidoreductase, fad binding protein, flavoprotein, cytokinin oxidase/dehydrogenase, cytokinin binding
• Biological source: Zea mays (maize)
• Total number of polymer chains: 2
• Total formula weight: 115889.04

Authors

Morera, S.,Kopecny, D.,Briozzo, P.,Koncitikova, R. (deposition date: 2013-09-06, release date: 2015-03-11, Last modification date: 2016-03-23)

Primary citation

Kopecny, D.,Koncitikova, R.,Popelka, H.,Briozzo, P.,Vigouroux, A.,Kopecna, M.,Zalabak, D.,Sebela, M.,Skopalova, J.,Frebort, I.,Morera, S.
Kinetic and structural investigation of the cytokinin oxidase/dehydrogenase active site.
Febs J., 283:361-377, 2016

PubMed Abstract: Cytokinins are hormones that regulate plant development and their environmental responses. Their levels are mainly controlled by the cytokinin oxidase/dehydrogenase (CKO), which oxidatively cleaves cytokinins using redox-active electron acceptors. CKO belongs to the group of flavoproteins with an 8α-N1-histidyl FAD covalent linkage. Here, we investigated the role of seven active site residues, H105, D169, E288, V378, E381, P427 and L492, in substrate binding and catalysis of the CKO1 from maize (Zea mays, ZmCKO1) combining site-directed mutagenesis with kinetics and X-ray crystallography. We identify E381 as a key residue for enzyme specificity that restricts substrate binding as well as quinone electron acceptor binding. We show that D169 is important for catalysis and that H105 covalently linked to FAD maintains the enzyme's structural integrity, stability and high rates with electron acceptors. The L492A mutation significantly modulates the cleavage of aromatic cytokinins and zeatin isomers. The high resolution X-ray structures of ZmCKO1 and the E381S variant in complex with N6-(2-isopentenyl)adenosine reveal the binding mode of cytokinin ribosides. Those of ZmCKO2 and ZmCKO4a contain a mobile domain, which might contribute to binding of the N9 substituted cytokinins.

PubMed: 26519657
DOI: 10.1111/febs.13581

Experimental method

X-RAY DIFFRACTION (2.04 Å)