Study On Partial Structure Of Wheat PGIP And Comparison Between Wheat PGIP And Dicotyledon PGIPs

Partial structure of wheat PGIP was studied in four aspect: deglycosylation, analysis of partial primary structure, secondary structure and disulfide bond.Wheat PGIP was deglycosylated using TFMS, and the result indicates that carbohydrates content is 22%, which is consist with PGIPs from dicotyledon. After deglycosylated, wheat PGTP could not interact with antibody produced by purified native PGtP from wheat. It is the glycans of wheat PGIP that probably fonn the epitope.The N-terminal amino acid sequence of PGIP from wheat was determined. The result was: Lys-Pro-Leu-Leu-Thr-Lys-Ile-Thr-Lys-Gly-Ala-Ala-Ser-Thr. It is the first time that the primary structure of wheat PGIP, even of monocotyledon PGIP, is reported. The N-terminal sequence of PGIPs in dicotyldonous plants shared 36% identical amino acids, but the percentage of overall identity was reduced to only 9% when wheat PGIP was included in the analysis. The cDNA encoding wheat PGIP could not be amplificated by primers based on the N-terminal sequence of wheat PGIP and the conserve C-terminal sequence of dicotyledon PGIPs. It is possible that the conserve sequence of dicotyledon PGIPs may be absent in PGIP from wheat, a monocotyledon.The secondary structure of wheat PGIP was first obtained by the measurement of circular dichroic spectra. The native PGIP of wheat was estimated to contain about 43.7% P -sheet and 13.1% a -helix. Moreover, the activity of wheat PGIP is related to P -sheet during denaturation by pH and temperature. It is similar to bean PGIPs.Wheat PGIP had disulfide bond within chains by analysis of NR/R two-dimensional electrophoresis. The disulfide bond with in chains is also existed in bean PGIPs.In conclusion, PGIPs from Wheat and dicotyledon are consistent in carbohydrates content, secondary structure and disulfide bond, but different in primary structure.The study on structure of wheat PGIP lay the foundation for the elucidation of its mechanism, and is significant for breeding crops resistant to Gibberella zeae (Schw.) Petch.