title: Purification of a trypsin inhibitor (PFTI) from pumpkin fruit phloem exudate and isolation of putative trypsin and chymotrypsin inhibitor cDNA clones.
abstract: The major trypsin inhibitor from pumpkin (Cucurbita maxima cv Supermarket Hybrid) fruit phloem exudate was purified by affinity and reverse phase chromatography. The protein has a molecular weight of approximately 8100 by SDS-PAGE and is blocked at the N-terminal serine. Following sequencing of a CNBr fragment, 3'- and 5'-RACE were used to isolate full length cDNAs corresponding to a trypsin inhibitor and to two chymotrypsin inhibitors. The three genes are similar, both in their translated and non-translated regions. Comparison of the full length translated proteins show that they are members of the proteinase inhibitor I family and almost identical apart from the P1 site in the proteinase binding loop. The genes encode proteins of 67 amino acids and appear to lack not only both pre- and prepro-peptide sequences but also the single disulphide present in most proteinase inhibitor I family members.
authors.affiliation: Pest Resistance Group, Horticulture and Food Research Institute of New Zealand, Palmerston North.
authors.forename: C
authors.initials: C
authors.lastname: Murray
authors.forename: J T
authors.initials: JT
authors.lastname: Christeller
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002846:Chromatography, Affinity; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005122:Exudates and Transudates / Q000737:chemistry*; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010944:Plants / Q000737:chemistry*; D016133:Polymerase Chain Reaction; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D018744:DNA, Plant; D015345:Oligonucleotide Probes; D014361:Trypsin Inhibitors; D002918:Chymotrypsin