Functional similarities of recombinant OLP and cytokinin-binding protein 2.

ABSTRACT

CBP1 and CBP2 are cytokinin-binding proteins isolated from tobacco callus. In particularly, CBP2 is a 26-kDa protein with high affinity (Kd=1.08 x 10(-6) M) for cytokinin [Kobayashi et al. Plant Cell Physiol.41(2) 148-157 (2000)] and the N-terminal amino acid analysis of CBP2 showed high sequence homology (92.9%) to tobacco osmotin-like protein (OLP). To compare the properties of OLP and CBP2, recombinant OLP was purified, and binding to benzyladenine (BA) was examined. The inclusion bodies of recombinant OLP were solubilized in 8 M urea and purified on an SP-Sepharose column. SDS-PAGE analysis of the purified recombinant OLP revealed a single band of 26 kDa. The Kd of solublized recombinant OLP to BA obtained from a Scatchard plot was 1.10 x 10(-6) M, which was similar to the Kd of CBP2 to BA (1.08 x 10(-6) M).