PURIFICATION AND N-TERMINAL SEQUENCE OF THE MAJOR LEAF PROTEIN (TRIFOLIATIN) FROM TRIFOLIATE ORANGE

The major protein found in the leaves, bark and hardened roots of trif oliate orange (Poncirus trifoliata L. Raf.) is a glycoprotein (M(r) 24 000). Characteristics of trifoliate orange protein, now called trifol iatin, are consistent with those reported for other plant storage prot eins, the low sequence similarity with other leaf proteins indicates t hat trifoliatin may represent a new class of vegetative proteins. Leve ls of glycoprotein vary inversely with leaf age and temperature [6] an d can reach levels up to 65% of total leaf protein. The purification o f this protein was accomplished by a combination of free zone isoelect ric focusing and chromatography techniques. The N-terminal sequence de termined by Edman (P. Edman and G. Begg, Fur. J. Biochem., 1 (1967) 80 ) degradation shares little to no sequence similarity with other known leaf proteins. The partial sequence of trifoliatin has the highest se quence similarity with sporamin, the major tuberous root storage prote in in sweet potato. Trifoliatin has no protease activity to casein hyd rolysate or inhibitory activity to trypsin or alpha-chymotrypsin.