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Polygalacturonase inhibitor proteins (PGIPs), also known as polygalacturonase-inhibiting proteins, are plant proteins capable of inhibiting the action of polygalacturonase (PG) enzymes produced by bacterial and fungal pathogens. PGs can be produced by pathogens to degrade the polygalacturonan component of plant cell walls. PGIPs are leucine-rich repeat glycoproteins of approximately 360 amino acids in length, and PGIPs may reduce the activity of PGs by one or two orders of magnitude. Both competitive and non-competitive inhibition has been observed for various PGIPs. However, no inhibition of endogenous plant PGs that participate in fruit ripening by PGIPs have been reported.

Small oligosaccharides produced from PG activity act as signals for the production of PGIPs within the plant. Despite the fact that most plant PGIPs have similar amino acids sequences, there exists a great deal of specificity between different plant and pathogen pairings. The specificity of the PGIPs for certain pathogenic PGs may significantly contribute to different crops being susceptible or resistant to different bacterial and fungal infections.

Structure

At present only one plant PGIP structure has been experimentally determined. A non-glycosylated version of PGIP-2 from Phaseolus vulgaris (bean) was successfully crystallized and analyzed by X-ray diffraction in 2003. Computational modeling has been used since that time to generate theoretical three-dimensional structures for many commonly researched plants and crops using the bean PGIP-2 structure as a template. Additional research has been done to characterize the glycosylations of various PGIPs, and these have been included in the computational models.

References

1. Darvill, A., Bergmann, C., Cervone, F., De Lorenzo, G., Ham, K.-S., Spiro, M. D., York, W. S., and Albersheim, P. (1994) Oligosaccharins involved in plant growth and host-pathogen interactions, Biochem. Soc. Symp. 60, 89-94.
2. Jones, T. M., Anderson, A. J., and Albersheim, P. (1972) Hostpathogen interactions IV, Studies on the polysaccharide-degrading enzymes secreted by Fusarium oxysporum f. sp. lycopersici, Physiol. Plant Pathol. 2, 153-166.
3. Cook, B. J., Clay, R. P., Bergmann, C. W., Albersheim, P., and Darvill, A. G. (1999) Fungal polygalacturonases exhibit different substrate degradation patterns and differ in their susceptibilities to polygalaturonase inhibiting proteins, Mol. Plant-Microbe Interact. 12, 703-711.
4. Federici L, Caprari C, Mattei B, Savino C, Di Matteo A, De Lorenzo G, Cervone F, Tsernoglou D. Structural requirements of endopolygalacturonase for the interaction with PGIP (polygalacturonase-inhibiting protein). Proc Natl Acad Sci U S A. 2001 Nov 6;98(23):13425-30.
5. Daniel King, Carl Bergmann, Ron Orlando, Jacques A. E. Benen, Harry C. M. Kester, and Jaap Visser; “Use of Amide Exchange Mass Spectrometry To Study Conformational Changes within the Endopolygalacturonase II – Polygalacturonic Acid – Polygalacturonase Inhibiting Protein System”, Biochem. 41, 10225-10233, 2002.
6. Hahn, M. G., Bucheli, P., Cervone, F., Doares, S. H., O’Neill, R. A., Darvill, A., and Albersheim, P. (1989) The Roles of Cell Wall Constituents in Plant-Pathogen Interactions, in Plant-Microbe Interactions. Molecular and Genetic PerspectiVes (Kosuge, T., and Nester, E. W., Eds.) Vol. 3, pp 131-181, McGraw-Hill, New York.
7. Cervone, F., De Lorenzo, G., Salvi, G., Bergmann, C., Hahn, M. G., Ito, Y., Darvill, A., and Albersheim, P. (1989) Release of Phytoalexin Elicitor-Active Oligogalacturonides by Microbial Pectic Enzymes, in Signal Molecules in Plants and Plant-Microbe Interactions (Lugtenberg, B. J. J., Ed.) NATO ASI Series, Vol. H36, pp 85-89, Springer-Verlag, Heidelberg, Germany.
8. Stotz, H. U., Bishop, J. G., Bergmann, C. W., Koch, M., Albersheim, P., Darvill, A. G., and Labavitch, J. M. (2000) Identification of target amino acids that affect interactions of fungal polygalacturonases and their plant inhibitors, Physiol. Mol. Plant Pathol. 56, 117-130.
9. Leckie, F., Mattei, B., Capodicasa, C., Hemmings, A., Nuss, L., Aracri, B., De Lorenzo, G., and Cervone, F. (1999) The specificity of polygalacturonase-inhibiting protein (PGIP): a single amino acid substitution in the solvent-exposed â-strand/â-turn region of the leucine-rich repeats (LRRs) confers a new recognition capability, EMBO J. 18, 2352-2363.
10. A. Di Matteo, L. Federici, B. Mattei, G. Salvi, K.A. Johnson, C. Savino, G. De Lorenzo, D. Tsernoglou, F. Cervone, “The Crystal Structure of Polygalacturonase-Inhibiting Protein (Pgip), A Leucine-Rich Repeat Protein Involved in Plant Defense”. Proc. Natl. Acad. Sci. USA, 100, 10124, 2003
11. Jae-Min Lim, Kazuhiro Aoki, Peggi Angel, Derek Garrison, Daniel King, Michael Tiemeyer, Carl Bergmann, and Lance Wells, “Mapping Glycans onto Specific N-Linked Glycosylation Sites of Pyrus Communis PGIP Redefines the Interface for EPG:PGIP Interactions”, Journal of Proteome Research, 8, 673-680, 2009
12. PG & PGIP Structural Database, http://www.pg-pgip.info

External links

• PG & PGIP Structural Database
• Pectinase Database

• Hydrolase inhibitors