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Plant Communications Apr 2024Cytokinins are a type of mobile phytohormone that regulate plant growth, development, and environmental adaptability. The major cytokinin species include isopentenyl... (Review)
Review
Cytokinins are a type of mobile phytohormone that regulate plant growth, development, and environmental adaptability. The major cytokinin species include isopentenyl adenine (iP), trans-zeatin (tZ), cis-zeatin (cZ), and dihydrozeatin (DZ). The spatial distributions of different cytokinin species in different organelles, cells, tissues, and organs are primarily shaped by biosynthesis via isopentenyltransferases (IPT), cytochrome P450 monooxygenase, and 5'-ribonucleotide phosphohydrolase, and by conjugation or catabolism via glycosyltransferase or cytokinin oxidase/dehydrogenase (CKX). Cytokinins bind to histidine receptor kinases (HKs) in the endoplasmic reticulum (ER) or plasma membrane (PM) and relay signals to response regulators (RRs) in the nucleus by shuttle proteins known as histidine phosphotransfer proteins (HPs). The movements of cytokinins from sites of biosynthesis to signal perception sites usually require long-distance, intercellular, and intracellular transport. In the past decade, ATP-binding cassette (ABC) transporters, purine permeases (PUP), AZA-GUANINE RESISTANT (AZG) transporters, equilibrative nucleoside transporters (ENT), and Sugars Will Eventually be Exported Transporters (SWEET) have been characterized as involved in cytokinin transport processes. This review begins by introducing the spatial distributions of various cytokinins and the subcellular localizations of the proteins involved in cytokinin metabolism and signaling. Highlights focus on an inventory of the characterized transporters involved in cytokinin compartmentalization, including long-distance, intercellular, and intracellular transport, and the regulation of spatial distributions of cytokinins by environmental cues. Future directions for cytokinin research are also discussed.
PubMed: 38689499
DOI: 10.1016/j.xplc.2024.100936 -
European Biophysics Journal : EBJ Oct 20238-azaguanine is a triazolopyrimidine nucleobase analog possessing potent antibacterial and antitumor activities, and it has been implicated as a lead molecule in cancer...
8-azaguanine is a triazolopyrimidine nucleobase analog possessing potent antibacterial and antitumor activities, and it has been implicated as a lead molecule in cancer and malaria therapy. Its intrinsic fluorescence properties can be utilized for monitoring its interactions with biological polymers like proteins or nucleic acids. In order to better understand these interactions, it is important to know the tautomeric equilibrium of this compound. In this work, the tautomeric equilibrium of all natural neutral and anionic compound forms (except highly improbable imino-enol tautomers) as well as their methyl derivatives and ribosides was revealed by quantum chemistry methods. It was shown that, as expected, tautomers protonated at positions 1 and 9 dominate neutral forms both in gas phase and in aqueous solution. 8-azaguanines methylated at any position of the triazole ring are protonated at position 1. The computed vertical absorption and emission energies are in very good agreement with the experimental data. They confirm the validity of the assumption that replacing the proton with the methyl group does not significantly change the positions of absorption and fluorescence peaks.
Topics: Azaguanine; Spectrum Analysis; Protons; Proteins; Quantum Theory
PubMed: 37507591
DOI: 10.1007/s00249-023-01672-x