M. Kooijman et al., SPECTROSCOPIC CHARACTERIZATION OF THE LIPID-BINDING PROPERTIES OF WHEAT PUROINDOLINES, Journal of cereal science, 26(2), 1997, pp. 145-159
The lipid-binding properties of wheat puroindolines (PINs) make these
proteins likely candidates to play an important role in the stability
of lipid films in die gas cells of bread dough, an important aspect of
bread making. Therefore, the interaction between PINs and water-solub
le model lipids was investigated by fluorescence emission and circular
dichroism (CD) spectroscopy. The secondary structure of PIN-a and PIN
-b in solution, as determined by far-UV CD measurements, resembled tha
t of plant non-specific lipid transfer protein (LTP). However, PINs co
ntain a tryptophan-rich loop located at the exterior of the protein. I
t was shown by fluorescence emission spectroscopy and near UV CD spect
roscopy that this domain is involved in the lipid binding. Fluorescenc
e titration experiments of PIN and its synthetic tryptophan-rich domai
ns with the zwitterionic lipid n-hexadecylphosphocholine (C16PN) revea
led that the binding was cooperative. For the binding of the charged l
ipids, n-hexadecacylphosphoglycol (C16PG) and hexadecyl-trimethylammon
iumbromide (CTAB), a clear effect of ionic strength of the solution wa
s obtained. Organisation of lipids into micelles Tvas not a prerequisi
te For binding to PINs. Most likely, wheat PIN binds to monomeric lipi
d molecules via its tryptophan-rich domain, rendering the protein more
hydrophobic. The overall secondary structure of wheat PINs did not ch
ange significantly upon binding to lipids. (C) 1997 Academic Press Lim
ited.