Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: December 17, 2001
Publication Date: March 20, 2002
Citation: FISH, W.W. THE ISOLATION AND CHARACTERIZATION OF CANTALOUPE FRUIT POLYGALACTURONASE- INHIBITING PROTEIN. FEDERATION OF AMERICAN SOCIETIES FOR EXPERIMENTAL BIOLOGY CONFERENCE. 2002. 16, 150.1. Technical Abstract: Polygalacturonase-inhibiting proteins (PGIPs) are believed to aid in plant defense against fungal pathogens by inhibiting polygalacturonase(s) (PG) secreted by the invading fungus. In an effort to better understand this type of plant-pathogen interaction in cantaloupe, we have isolated cantaloupe PGIP (C-PGIP) to ~95% electrophoretic purity from 5-15 day postanthesis cantaloupe fruit. The electrophoretic band of C-PGIP stained for both protein and carbohydrate. C-PGIP inhibited crude extracts of PG from two of three cantaloupe fungal pathogens tested. Results from viscometric and spectrophotometric assays for PG activity in the presence or absence of C-PGIP were consistent with C-PGIP inhibition of endo-PG activity. The MW of C-PGIP by sedimentation equilibrium or MALDI-TOE MS was 38,500. The pI of C-PGIP >9.5 and its E**1% at 280nm was 0.72. Native C-PGIP exhibited pronounced ellipticity in its near uv circular dichroism (cd) spectrum and possessed a far uv cd spectrum indicative of B-sheet periodic structure. The amino acid sequence of the first 23 residues at the N-terminus of C-PGIP exhibited 65% homology to apple and pear PGIPs and 56% homology to bean and tomato PGIPs.