TY - JOUR
T1 - Nucleotide availability in maize (Zea mays L.) root tips
T2 - Estimation of free and protein-bound nucleotides using 31P-nuclear magnetic resonance and a novel protein-ligand-binding assay
AU - Hooks, Mark A.
AU - Shearer, Gregory C.
AU - Roberts, Justin K.M.
PY - 1994/2
Y1 - 1994/2
N2 - Sequestration of nucleotides in cells through protein binding could influence the availability of nucleotides and free energy for metabolic reactions and, therefore, affect rates of physiological processes. We have estimated the proportion of nucleotides bound to proteins in maize (Zea mays L.) root tips. Binding of nucleoside mono- and diphosphates to total root-tip protein was studied in vitro using high-performance liquid chromatography and a new ligand-binding technique. We estimate that approximately 40% of the ADP, 65% of the GDP, 50% of the AMP, and virtually all the GMP in aerobic cells are bound to proteins. In hypoxic cells, free concentrations of these nucleotides increase proportionately much more than total intracellular concentrations. Little or no binding of CDP, UDP, CMP, and UMP was observed in vitro. Binding of nucleoside triphosphate (NTP) to protein was estimated from in vivo 31P-nuclear magnetic resonance relaxation measurements. In aerobic root tips most (approximately 70%) of the NTP is free, whereas under hypoxia NTP appears predominantly bound to protein. Our results indicate that binding of nucleotides to proteins in plant cells will significantly influence levels of free purine nucleotides available to drive and regulate respiration, protein synthesis, ion transport, and other physiological processes.
AB - Sequestration of nucleotides in cells through protein binding could influence the availability of nucleotides and free energy for metabolic reactions and, therefore, affect rates of physiological processes. We have estimated the proportion of nucleotides bound to proteins in maize (Zea mays L.) root tips. Binding of nucleoside mono- and diphosphates to total root-tip protein was studied in vitro using high-performance liquid chromatography and a new ligand-binding technique. We estimate that approximately 40% of the ADP, 65% of the GDP, 50% of the AMP, and virtually all the GMP in aerobic cells are bound to proteins. In hypoxic cells, free concentrations of these nucleotides increase proportionately much more than total intracellular concentrations. Little or no binding of CDP, UDP, CMP, and UMP was observed in vitro. Binding of nucleoside triphosphate (NTP) to protein was estimated from in vivo 31P-nuclear magnetic resonance relaxation measurements. In aerobic root tips most (approximately 70%) of the NTP is free, whereas under hypoxia NTP appears predominantly bound to protein. Our results indicate that binding of nucleotides to proteins in plant cells will significantly influence levels of free purine nucleotides available to drive and regulate respiration, protein synthesis, ion transport, and other physiological processes.
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U2 - 10.1104/pp.104.2.581
DO - 10.1104/pp.104.2.581
M3 - Article
AN - SCOPUS:0028092362
SN - 0032-0889
VL - 104
SP - 581
EP - 589
JO - Plant physiology
JF - Plant physiology
IS - 2
ER -