Journal of Genetics

, Volume 73, Issue 1, pp 43–54 | Cite as

Studies on molecular evolution and structural features of double-headed inhibitors of α-amylase and trypsin in plants

  • Sameer Velankar
  • M. R. N. Murthy
Article

Abstract

Plant seeds usually have high concentrations of proteinase and amylase inhibitors. These inhibitors exhibit a wide range of specificity, stability and oligomeric structure. In this communication, we report analysis of sequences that show statistically significant similarity to the double-headed α-amylase/trypsin inhibitor of ragi (Eleusine coracana). Our aim is to understand their evolutionary and structural features. The 14 sequences of this family that are available in the SWISSPROT database form three evolutionarily distinct branches. The branches relate to enzyme specificities and also probably to the oligomeric state of the proteins and not to the botanical class of the plant from which the enzymes are derived. This suggests that the enzyme specificities of the inhibitors evolved before the divergence of commercially cultivated cereals. The inhibitor sequences have three regions that display periodicity in hydrophobicity. It is likely that this feature reflects extended secondary structure in these segments. One of the most variable regions of the polypeptide corresponds to a loop, which is most probably exposed in the native structure of the inhibitors and is responsible for the inhibitory property.

Keywords

Inhibitors sequence comparison evolution trypsin amylase 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Campos F. A. P. and Richardson M. 1983 The complete amino acid sequence of the bifunctional α-amylase/trypsin inhibitor from seeds of ragi (Eleusine coracana).FEBS Lett. 152: 300–304CrossRefGoogle Scholar
  2. Cockerill M. 1993 Not much to malign.Trends Biochem. Sci. 18: 106–107CrossRefGoogle Scholar
  3. Desai N. and Bourne P., 1986 Protein and nucleic acid sequence information and analysis, PRONUC version 4.4, Columbia University, New YorkGoogle Scholar
  4. Doolittle R. F. 1979 Protein evolution. InThe proteins, 2nd edition (eds.) H. Neurath and R. C. Hill (New York: Academic Press) vol. 4, pp. 1–118Google Scholar
  5. Kyte J. and Doolittle R. F. 1982 A simple method for displaying the hydropathic character of a protein.J. Mal. Biol. 157: 105–132CrossRefGoogle Scholar
  6. Laskowski M.Jr. and Kato I. 1980 Protein inhibitors of proteinases.Annu. Rev. Biochem. 49: 593–626PubMedCrossRefGoogle Scholar
  7. Maeda K., Hase T. and Malsubara H. 1983 Complete amino acid sequence of an α-amylase inhibitor in wheat kernel.Biochim. Biophys. Acta 743: 52–57PubMedGoogle Scholar
  8. Maeda K., Kakabayashi S. and Matsubara H. 1985 Complete amino acid sequence of an α-amylase inhibitor in wheat kernel (019 inhibitor).Biochim. Biophys. Acta 828: 213–221PubMedGoogle Scholar
  9. Mahoney W. C., Hermodson M. A., Jones B., Powers B. D., Corfman R. S. and Reeck G. R. 1984 Amino acid sequence and secondary structural analysis of the corn inhibitor of trypsin and activated Hageman factor.J. Biol. Chem. 259: 8412–8416PubMedGoogle Scholar
  10. Needleman S. B. and Wunsch C. D. 1970 A general method applicable to the search for similarities in the amino acid sequence of two proteins.J. Mol. Biol. 48: 443–453PubMedCrossRefGoogle Scholar
  11. Pearson W. R. 1990 Rapid and sensitive sequence comparison with FASTP and FASTA.Methods Enzymol. 183: 63–98PubMedCrossRefGoogle Scholar
  12. Pearson W. R. and Lipman D. J. 1988 Improved tools for biological sequence comparison.Proc. Natl. Acad. Sci. USA 85: 2444–2448PubMedCrossRefGoogle Scholar
  13. Schwartz R. M. and Dayhoff M. O. 1978 Matrices for detecting distance relationships. InAtlas of protein sequence and structure (ed.) M. O. Dayhoff (Washington, D. C: National Biomedical Research Foundation) vol. 5, pp. 353–358Google Scholar
  14. Shivaraj B. and Pattabhiraman T. N. 1980 Natural plant enzyme inhibitors: Part VIII—Purification and properties of two α-amylase inhibitors from ragi (Eleusine coracana) grains.Indian J. Biochem. Biophys. 17: 181–185Google Scholar
  15. Shivaraj B. and Pattabhiraman T. N. 1981 Natural plant enzyme inhibitors.Biochem. J. 193: 29–36PubMedGoogle Scholar
  16. Shivaraj B., Rao Nayana H. and Pattabhiraman T. N. 1982 Natural plant enzyme inhibitors. Isolation of trypsin/α-amylase inhibitor and a chymotrypsin/trypsin inhibitor from ragi (Eleusine coracana) grains by affinity chromatography and study of their properties.J. Sci. Food Agric. 33: 1080–1091CrossRefGoogle Scholar
  17. Sweet R. M., Wright H. T., Janin J., Chothia C. H. and Blow D. M. 1974 Crystal structure of the complex of porcine trypsin with soybean trypsin inhibitor (Kunitz) at 2.6 Å resolution.Biochemistry 13: 4212–4228PubMedCrossRefGoogle Scholar

Copyright information

© Indian Academy of Sciences 1994

Authors and Affiliations

  • Sameer Velankar
    • 1
  • M. R. N. Murthy
    • 1
  1. 1.Molecular Biophysics UnitIndian Institute of ScienceBangaloreIndia

Personalised recommendations