PURIFICATION AND PARTIAL CHARACTERIZATION OF A GLYCOPROTEIN FROM PEA (PISUM-SATIVUM) WITH RECEPTOR ACTIVITY FOR RHICADHESIN, AN ATTACHMENT PROTEIN OF RHIZOBIACEAE
S. Swart et al., PURIFICATION AND PARTIAL CHARACTERIZATION OF A GLYCOPROTEIN FROM PEA (PISUM-SATIVUM) WITH RECEPTOR ACTIVITY FOR RHICADHESIN, AN ATTACHMENT PROTEIN OF RHIZOBIACEAE, Plant molecular biology, 24(1), 1994, pp. 171-183
Attachment of Rhizobium and Agrobacterium bacteria to cells of their h
ost plants is a two-step process. The first step, direct attachment of
bacteria to the plant cell wall, is mediated by the bacterial protein
rhicadhesin. A putative plant receptor molecule for rhicadhesin was p
urified from cell walls of pea roots using a bioassay based on suppres
sion of rhicadhesin activity. This molecule appeared to be sensitive t
o treatments with pronase or glycosidase. Its isoelectric point is 6.4
, and its apparent molecular mass was estimated to be 32 kDa before an
d 29 kDa after glycosidase treatment, as determined by sodium dodecyl
sulphate-polyacrylamide gel electrophoresis and ultrafiltration. The s
equence of the first 29 N-terminal amino acids was determined: D-L-C(?
)-V-A-D-Y-A-S-V-I-L-V-N-G-F-A-S-K(Q)-(P/Q)- (L)-(I). No homology with
known proteins was found. In the course of this research project the e
xtracellular matrix protein vitronectin was reported to inhibit attach
ment of A. tumefaciens to carrot cells [29]. A variety of adhesive pro
teins, including vitronectin, contain a common cell attachment determi
nant with the sequence R-G-D. Since we could not detect other cell wal
l components able to suppress rhicadhesin activity, and since an R-G-D
containing hexapeptide was also active as a receptor, we speculate th
at the plant receptor for rhicadhesin is a glycoprotein containing an
R-G-D attachment site.