Purification and characterization of a wound-inducible thaumatin-like protein from the latex of Carica papaya.
A 22.137 kDa protein constituent of fresh latex was isolated both from the latex of regularly damaged papaya trees and from a commercially available papain preparation. The protein was purified up to apparent homogeneity and was shown to be absent in the latex of papaya trees that had never been previously mechanically injured. This suggests that the protein belongs to pathogenesis-related protein family, as expected for several other protein constituents of papaya latex. The protein was identified as a thaumatin-like protein (class 5 of the pathogenesis-related proteins) on the basis of its partial amino acid sequence. By sequence analysis of the Carica genome, three different forms of thaumatin-like protein were identified, where the latex constituent belongs to a well-known form, allowing the molecular modeling of its spatial structure. The papaya latex thaumatin-like protein was further characterized. The protein appears to be stable in the pH interval from 2 to 10 and resistant to chemical denaturation by guanidium chloride, with a DeltaG(water)(0) of 15.2 kcal/mol and to proteolysis by the four papaya cysteine proteinases. The physiological role of this protein is discussed.
Looze
Yvan
Y
Laboratoire de Chimie Générale (CP: 206/4), Institut de Pharmacie, Université Libre de Bruxelles, Campus de la Plaine, Boulevard du Triomphe, 1050 Brussels, Belgium.
Boussard
Paule
P
Huet
Joëlle
J
Vandenbusche
Guy
G
Vandenbussche
Guy
G
Azarkan
Mohamed
M
Raussens
Vincent
V
Wintjens
René
R
D000595:Amino Acid Sequence; D029441:Carica / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D007840:Latex / Q000737:chemistry / Q000302:isolation & purification*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification*; D011487:Protein Conformation; D014947:Wounds and Injuries / Q000503:physiopathology
D007840:Latex; D010940:Plant Proteins; C542356:latex thaumatin-like protein, papaya; C003427:thaumatin protein, plant