R. Girault et al., Identification and partial characterization of proteins and proteoglycans encrusting the secondary cell walls of flax fibres, PLANTA, 211(2), 2000, pp. 256-264
Four proteins were isolated from depectinised elementary fibres of flax (Li
num usitatissimum L.), using either alkali or cellulase digestion treatment
s. All the four proteins were characterized by a deficiency or low contents
of hydroxyproline and by high levels of glutamic acid/glutamine and/or asp
artic acid/asparagine. The two proteoglycans solubilized with cellulase str
ongly reacted with beta-glucosyl Yariv reagent but not with alpha-glucosyl
Yariv reagent and contained appreciable amounts of alanine, glycine, serine
and threonine, suggesting a relationship with cell wall hydroxyproline def
icient arabinogalactan-proteins. The two alkali-extracted proteins did not
show beta-glucosyl Yariv dye. Due to the harsh treatment, they might only p
artially represent the original proteins. Due to its high level of glycine
(41%), one of these proteins might be classified as a glycine-rich protein.
The latter porypeptide, of low molecular molar mass, contained 14.6% leuci
ne and might consist of a domain related to leucine-rich proteins. The data
show that these proteins and arabinogalactan-protein-like proteoglycans we
re strongly associated with the secondary walls of flax fibres. Their prese
nce in small amounts (0.1-0.4%), raises the problem of their putative struc
tural role.