A major wall
protein of
suspension-cultured cells of French bean has been isolated and characterised. It can be prepared from walls or the culture filtrate and in composition it is particularly rich in
proline,
valine and
glutamic acid/
glutamine and contains appreciable amounts of
hydroxyproline. The N-terminus shows some glycosylation, while following chemical deglycosylation the first 38 residues were found to be identical to those of
proline-rich
proteins from soybean. However, the composition of the highly purified Mr-42000 bean
protein differs considerably from the
soybean proteins and must contain its own specific domains. An antibody was raised and used to demonstrate the inducibility of the Mr-42000 bean
protein in response to elicitor action. The
protein was found to be mainly localised in the intercellular spaces of the cortical cells of bean hypocotyls and at the wall-plasmalemma interface of xylem vessels, another potentially accessible compartment for pathogens. Following wounding, the
protein was found to be generally distributed in the wall of epidermal and cortical cells of the hypocotyls. The Mr-42000
protein is cross reactive with
antibodies raised to
glycoproteins of the Rhizobium
infection thread and the
chitin-binding
hydroxyproline-rich
glycoprotein,
potato lectin. These common
epitopes together with the previously demonstrated
chitin-binding properties of the bean
protein indicate a role in host-microbial interactions. Furthermore, the Mr-42000
protein itself bound to the growing hyphal
tips of the bean pathogen, Colletotrichum lindemuthianum.