A chimera of Urtica dioica agglutinin and tobacco chitinase displays both agglutination and chitinase activity

To obtain a protein with agglutination activity as well as chitinase activi ty, a fusion protein was designed in which Urtica dioica agglutinin (UDA)-i solectin I and the catalytic domain of tobacco (Nicotiana tabacum cv. Samsu n NN) chitinase I were assembled. A, construct was made containing sequence s encoding the signal peptide and the isolectin sequence of the precursor t o UDA-isolectin I, followed by the linker and the catalytic domain of tobac co chitinase I. Due to the introduction of a stopcodon, the precursor to th is chimera lacked the seven carboxyl-terminal amino acids necessary for vac uolar targeting of tobacco chitinase I. The construct was expressed in tran sgenic tobacco (Nicotiana tabacum cv. Samsun NN) under control of the cauli flower mosaic virus 35S promoter. Analysis of transgenic plants showed that the fusion protein UDA-Chi is targeted extracellularly. Both crude leaf ex tracts of transgenic tobacco and purified fusion protein showed agglutinati on activity on trypsin-treated rabbit erythrocytes. The molar agglutination activity of the UDA-Chi chimera was shown to be similar to that of mature UDA. The chimera has chitinase activity that differs from that of tobacco c hitinase I. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.