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. 1997 Dec;115(4):1481–1489. doi: 10.1104/pp.115.4.1481

Protein repair L-isoaspartyl methyltransferase in plants. Phylogenetic distribution and the accumulation of substrate proteins in aged barley seeds.

M B Mudgett 1, J D Lowenson 1, S Clarke 1
PMCID: PMC158613  PMID: 9414558

Abstract

Protein L-isoaspartate (D-aspartate) O-methyltransferases (MTs; EC 2.1.1.77) can initiate the conversion of detrimental L-isoaspartyl residues in spontaneously damaged proteins to normal L-aspartyl residues. We detected this enzyme in 45 species from 23 families representing most of the divisions of the plant kingdom. MT activity is often localized in seeds, suggesting that it has a role in their maturation, quiescence, and germination. The relationship among MT activity, the accumulation of abnormal protein L-isoaspartyl residues, and seed viability was explored in barley (Hordeum vulgare cultivar Himalaya) seeds, which contain high levels of MT. Natural aging of barley seeds for 17 years resulted in a significant reduction in MT activity and in seed viability, coupled with increased levels of "unrepaired" L-isoaspartyl residues. In seeds heated to accelerate aging, we found no reduction of MT activity, but we did observe decreased seed viability and the accumulation of isoaspartyl residues. Among populations of accelerated aged seed, those possessing the highest levels of L-isoaspartyl-containing proteins had the lowest germination percentages. These results suggest that the MT present in seeds cannot efficiently repair all spontaneously damaged proteins containing altered aspartyl residues, and their accumulation during aging may contribute to the loss of seed viability.

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Selected References

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  1. Bostock R. M., Quatrano R. S. Regulation of Em Gene Expression in Rice : Interaction between Osmotic Stress and Abscisic Acid. Plant Physiol. 1992 Apr;98(4):1356–1363. doi: 10.1104/pp.98.4.1356. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Brennan T. V., Anderson J. W., Jia Z., Waygood E. B., Clarke S. Repair of spontaneously deamidated HPr phosphocarrier protein catalyzed by the L-isoaspartate-(D-aspartate) O-methyltransferase. J Biol Chem. 1994 Oct 7;269(40):24586–24595. [PubMed] [Google Scholar]
  3. Brennan T. V., Clarke S. Spontaneous degradation of polypeptides at aspartyl and asparaginyl residues: effects of the solvent dielectric. Protein Sci. 1993 Mar;2(3):331–338. doi: 10.1002/pro.5560020305. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Galletti P., Ciardiello A., Ingrosso D., Di Donato A., D'Alessio G. Repair of isopeptide bonds by protein carboxyl O-methyltransferase: seminal ribonuclease as a model system. Biochemistry. 1988 Mar 8;27(5):1752–1757. doi: 10.1021/bi00405a055. [DOI] [PubMed] [Google Scholar]
  5. Harding J. J. Nonenzymatic covalent posttranslational modification of proteins in vivo. Adv Protein Chem. 1985;37:247–334. doi: 10.1016/s0065-3233(08)60066-2. [DOI] [PubMed] [Google Scholar]
  6. Johnson B. A., Langmack E. L., Aswad D. W. Partial repair of deamidation-damaged calmodulin by protein carboxyl methyltransferase. J Biol Chem. 1987 Sep 5;262(25):12283–12287. [PubMed] [Google Scholar]
  7. Johnson B. A., Ngo S. Q., Aswad D. W. Widespread phylogenetic distribution of a protein methyltransferase that modifies L-isoaspartyl residues. Biochem Int. 1991 Jul;24(5):841–847. [PubMed] [Google Scholar]
  8. Kagan R. M., Clarke S. Protein L-isoaspartyl methyltransferase from the nematode Caenorhabditis elegans: genomic structure and substrate specificity. Biochemistry. 1995 Aug 29;34(34):10794–10806. doi: 10.1021/bi00034a012. [DOI] [PubMed] [Google Scholar]
  9. Kim E., Lowenson J. D., MacLaren D. C., Clarke S., Young S. G. Deficiency of a protein-repair enzyme results in the accumulation of altered proteins, retardation of growth, and fatal seizures in mice. Proc Natl Acad Sci U S A. 1997 Jun 10;94(12):6132–6137. doi: 10.1073/pnas.94.12.6132. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Li C., Clarke S. Distribution of an L-isoaspartyl protein methyltransferase in eubacteria. J Bacteriol. 1992 Jan;174(2):355–361. doi: 10.1128/jb.174.2.355-361.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Lowenson J. D., Clarke S. Structural elements affecting the recognition of L-isoaspartyl residues by the L-isoaspartyl/D-aspartyl protein methyltransferase. Implications for the repair hypothesis. J Biol Chem. 1991 Oct 15;266(29):19396–19406. [PubMed] [Google Scholar]
  12. MacLaren D. C., Clarke S. Expression and purification of a human recombinant methyltransferase that repairs damaged proteins. Protein Expr Purif. 1995 Feb;6(1):99–108. doi: 10.1006/prep.1995.1013. [DOI] [PubMed] [Google Scholar]
  13. Mudgett M. B., Clarke S. A distinctly regulated protein repair L-isoaspartylmethyltransferase from Arabidopsis thaliana. Plant Mol Biol. 1996 Feb;30(4):723–737. doi: 10.1007/BF00019007. [DOI] [PubMed] [Google Scholar]
  14. Mudgett M. B., Clarke S. Characterization of plant L-isoaspartyl methyltransferases that may be involved in seed survival: purification, cloning, and sequence analysis of the wheat germ enzyme. Biochemistry. 1993 Oct 19;32(41):11100–11111. doi: 10.1021/bi00092a020. [DOI] [PubMed] [Google Scholar]
  15. Mudgett M. B., Clarke S. Hormonal and environmental responsiveness of a developmentally regulated protein repair L-isoaspartyl methyltransferase in wheat. J Biol Chem. 1994 Oct 14;269(41):25605–25612. [PubMed] [Google Scholar]
  16. Parrish D. J., Leopold A. C. On the mechanism of aging in soybean seeds. Plant Physiol. 1978 Mar;61(3):365–368. doi: 10.1104/pp.61.3.365. [DOI] [PMC free article] [PubMed] [Google Scholar]

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