Hypoxia enhances phosphorylation of eukaryotic initiation factor 4A in maize root tips
| Autor: | Rebecca L. Gaut, Cecelia Webster, Justin K. M. Roberts, Joanne M. Ravel, Karen S. Browning |
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| Rok vydání: | 1991 |
| Předmět: |
Gene isoform
Gel electrophoresis Phosphopeptide food and beverages macromolecular substances Cell Biology Biology environment and public health Biochemistry Molecular biology Phosphoamino acid analysis enzymes and coenzymes (carbohydrates) Isoelectric point Initiation factor Phosphorylation heterocyclic compounds Threonine Molecular Biology |
| Zdroj: | Journal of Biological Chemistry. 266:23341-23346 |
| ISSN: | 0021-9258 |
| DOI: | 10.1016/s0021-9258(18)54502-6 |
| Popis: | We have identified two isoforms of initiation factor 4A (eIF-4A) in maize root tips, with distinct isoelectric points and similar molecular mass (approximately 50 kDa). Both isoforms of maize eIF-4A cross-react with antibodies raised against wheat germ eIF-4A, and one of the maize proteins (higher pI isoform) comigrates with purified wheat germ eIF-4A on two-dimensional gels. The two maize eIF-4As were indistinguishable by comparative peptide fingerprint analysis, which also showed a very strong similarity between eIF-4A in maize roots and wheat germ. Maize eIF-4As copurify with eIF-4F and eIF-(iso)4F on a 7-methyl-GTP-Sepharose affinity column, indicating that they are part of the 5'-cap-binding complex. Two-dimensional gel electrophoresis and immunoblotting of proteins from 32P-labeled maize root tips revealed that the lower pI isoform of eIF-4A is phosphorylated. Two-dimensional phosphopeptide maps of trypsin-digested eIF-4A contained one principal phosphorylated fragment; phosphoamino acid analysis indicated phosphorylation of threonine. In oxygenated maize root tips, the ratio of phosphorylated to nonphosphorylated eIF-4A is approximately 0.2. This ratio increases to approximately 1 within 20 min following the onset of hypoxia, due to interconversion between the two maize eIF-4A isoforms. The hypoxia-induced phosphorylation of eIF-4A is discussed with respect to metabolic responses, and the translational control of gene expression, in hypoxic plant tissues. |
| Databáze: | OpenAIRE |
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