Electrochemical Study of the Lipid‐Transfer Protein

Abstract

Electrochemical study of barley grain lipid-transfer protein (LTP) revealed that it may belong to the metal-binding protein class. Using differential pulse polarography the presence of Cu(II) and Zn(II) ions in the native LTP structure was proved, as well as its affinity for binding Ni(II) ion. Application of a more sensitive electroanalytical technique, such as anodic stripping voltammetry with analyte preconcentration, revealed the presence of Pb(II) and Cd(II) ions and also enabled the following Hg(II) ion binding. Possible biological role of LTP in plant stress response and its contribution to barley phytoextraction potential are discussed.

Barley Grain Non-specific Lipid-Transfer Proteins (ns-LTPs) in Beer Production and Quality

“…Wheat ns-LTP2, whose sequence shows ∼77% identity with barley grain ns-LTP2, is composed of five helices, structured as a right superhelix 120 . The global structure of ns-LTP2 is similar to ns-LTP1; H1 (3-16), H2 (22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) and H5 (50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63) in ns-LTP2 are superimposed with H1, H2 and H4 helices in ns-LTP1 120 . Ns-LTP2 also consists of a hydrophobic cavity structure adapted to the lipid transport, but its cavity exhibits a different geometry than ns-LTP1s 128 .…”

“…The role of ns-LTP1 in seed and seedling protection is also supported by the finding that protein is synthesized de novo in the aleurone, at the onset of water uptake by the seeds, and secreted into the incubation medium 146 . Discovery that barley grain ns-LTP1 might belong to a metal-binding protein class suggests its possible role in protection against heavy metal ion exposure 59,60 . This hypothesis is consistent with the previous finding that ns-LTP1 synthesis is induced by heavy metal occurrence 71 , since localized extracellular ns-LTP1 could participate in heavy metal detoxification by immobilizing toxic metal ions, preventing their transport into the cell.…”

“…The original postulation that they are involved in intracellular transport of lipids between compartments, based on their ability to bind lipids in vitro, was contrasted by findings that they are extracellular secretory proteins. Currently, it is thought that they play several in vivo roles including the assembly of protective extracellular hydrophobic polymers (cutin and suberin) 71,141,155 , inhibition of bacterial and fungal pathogens 15,20,50,52,61,103,125,153 , the adaptation of plants to abiotic stresses (cold, salt, heavy metal exposure) 31,59,60,79,149 , the early recognition of pathogens, i.e. defense signaling 8,12,13,100 and inhibition of cysteine proteinases 76,77 .…”

A Review: The Role of Barley Seed Pathogenesis-Related Proteins (PRs) in Beer Production

“…It is a very clean product from a metal concentration point of view. Implications of the barley grain ns-LTP1 ability to bind toxic cations 55,56 in beer can probably be discarded. It is more likely that the ns-LTP1 present in beer does not have cationic binding ability.…”

A Review: Biological and Technological Functions of Barley Seed Pathogenesis-Related Proteins (PRs)

“…Although both ns-LTP1 and ns-LTP2 share high structural similarity with elicitin, only ns-LTP2 has the ability to bind sterol, which leads to the hypothesis that ns-LTP2, rather than ns-LTP1, could activate the plant response 58 . The theory concerning a barley seed ns-LTP1 role in heavy metal stress response is based on its ability to bind toxic cations 108,112 . As cysteine protease inhibitors, ns-LTP1 and ns-LTP2 could regulate proteolysis during germination, i.e., malting 160,161 .…”