Plant and Cell Physiology, 1985, Vol. 26, No. 6 1037-1044
© 1985
Article |
Presence of Serine Enzymes in Endoplasmic Reticulum of Spinach Callus
Institute of Biological Sciences, University of Tsukuba Sakura-mura, Ibaraki 305, Japan
Two serine enzymes were detected in microsomes of spinach callus by labeling with [3H]-di-isopropyl phosphorofluoridate (DFP) and examination by SDS-polyacrylamide gel electrophoresis. The contents of the larger (mol wt 44,000) and the smaller (mol wt 39,000) DFP-binding protein (proteins which have a DFP-reactive site) were maximum at the third and the second week after cell inoculation, respectively. The positions of both proteins on the continuous sucrose gradient coincided with that of NADH-cytochrome c reductase, a marker enzyme of the endoplasmic reticulum. The smaller protein was released from microsomes treated with 0.05% deoxycholate. The larger protein was solubilized with 0.5% cholate, but not with 0.05% deoxycholate, and the apparent molecular weight of the solubilized protein was about 90,000 in 0.5% cholate on Sephacryl S-200 column. [3H]-DFP-binding with the larger protein was strongly inhibited by DFP, phenylmethylsulfonyl fluoride, N-p-tosyl-L-lysine chloromethyl ketone and L-1-tosylamide-2-phenylethyl chloromethyl ketone, and slightly by p-chloromercuric benzoate and o-phenanthroline. DFP binding with the smaller one was strongly inhibited by DFP and PMSF, but not by other reagents.
(Received February 12, 1985; Accepted May 27, 1985)
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