This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.

Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.

3s1f

From Proteopedia

Jump to: navigation, search

Asp169Glu mutant of maize cytokinin oxidase/dehydrogenase complexed with N6-isopentenyladenine

Structural highlights

3s1f is a 1 chain structure with sequence from Zea mays. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2Å
Ligands:	, , , ,
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

CKX1_MAIZE Catalyzes the oxidation of cytokinins, a family of N(6)-substituted adenine derivatives that are plant hormones, where the substituent is an isopentenyl group. Cleaves zeatin, isopentenyladenine, isopentenyladenosine, zeatin riboside and cis-zeatin, but not dihydrozeatin, kinetin and benzylaminopurine.

Publication Abstract from PubMed

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 8alpha-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. Here, 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 (iPR) 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. This article is protected by copyright. All rights reserved.

Kinetic and structural investigation of the cytokinin oxidase/dehydrogenase active site.,Kopecny D, Koncitikova R, Popelka H, Briozzo P, Vigouroux A, Kopecna M, Zalabak D, Sebela M, Skopalova J, Frebort I, Morera S FEBS J. 2015 Oct 31. doi: 10.1111/febs.13581. PMID:26519657^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ 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. 2015 Oct 31. doi: 10.1111/febs.13581. PMID:26519657 doi:http://dx.doi.org/10.1111/febs.13581