Features and Possible Applications of Plant Lipid-Binding and Transfer Proteins

In plants, lipid trafficking within and inside the cell is carried out by lipid-binding and transfer proteins. Ligands for these proteins are building and signaling lipid molecules, secondary metabolites with different biological activities due to which they perform diverse functions in plants. Many different classes of such lipid-binding and transfer proteins have been found, but the most common and represented in plants are lipid transfer proteins (LTPs), pathogenesis-related class 10 (PR-10) proteins, acyl-CoA-binding proteins (ACBPs), and puroindolines (PINs). A low degree of amino acid sequence homology but similar spatial structures containing an internal hydrophobic cavity are common features of these classes of proteins. In this review, we summarize the latest known data on the features of these protein classes with particular focus on their ability to bind and transfer lipid ligands. We analyzed the structural features of these proteins, the diversity of their possible ligands, the key amino acids participating in ligand binding, the currently known mechanisms of ligand binding and transferring, as well as prospects for possible application.

A Review on the Source of Lipids and Their Interactions during Beer Fermentation that Affect Beer Quality

The presence of lipids in wort and beer are important due to their influence on yeast metabolism and beer quality. Barley lipids have long been considered to have adverse effects on beer quality where some long-chain fatty acids are associated with high flavour potential. In addition, beer foam stability can be influenced by the concentration of lipids as well as other factors such as hop acids (e.g., iso-α-acids), proteins, polysaccharides and the presence of metal ions (e.g., nickel). Lipids can also influence yeast protease activity as well as the production of ethanol. This review provides an overview of the effect of climate change on the chemical composition of barley in relation to lipids and the influence of lipids in the process of this raw material in order to produce beer.

Optimised purification and characterisation of lipid transfer protein 1 (LTP1) and its lipid-bound isoform LTP1b from barley malt

In beer brewing, brewers worldwide strive to obtain product consistency in terms of flavour, colour and foam. Important proteins contributing to beer foam are lipid transfer proteins (LTPs), in particular LTP1 and its lipid-bound isoform LTP1b, which are known to transport lipids in vivo and prevent lipids from destabilising the beer foam. LTP1 and LTP1b were successfully purified using only five purification steps with a high purified protein yield (160 mg LTP1 and LTP1b from 200 g barley). Circular dichroism of LTP1 and LTP1b confirmed that both proteins are highly tolerant to high temperatures (>90 °C) and are pH stable, particularly at a neutral to a more basic pH. Only LTP1 exhibited antiyeast and thermo-stable lytic activity, while LTP1b was inactive, indicating that the fatty acid moiety compromised the antimicrobial activity of LTP1. This lack in antiyeast activity and the positive foam properties of LTP1b would benefit beer fermentation and quality.

Long distance movement of DIR1 and investigation of the role of DIR1-like during systemic acquired resistance in Arabidopsis

DIR1 is a lipid transfer protein (LTP) postulated to complex with and/or chaperone a signal(s) to distant leaves during Systemic Acquired Resistance (SAR) in Arabidopsis. DIR1 was detected in phloem sap-enriched petiole exudates collected from wild-type leaves induced for SAR, suggesting that DIR1 gains access to the phloem for movement from the induced leaf. Occasionally the defective in induced resistance1 (dir1-1) mutant displayed a partially SAR-competent phenotype and a DIR1-sized band in protein gel blots was detected in dir1-1 exudates suggesting that a highly similar protein, DIR1-like (At5g48490), may contribute to SAR. Recombinant protein studies demonstrated that DIR1 polyclonal antibodies recognize DIR1 and DIR1-like. Homology modeling of DIR1-like using the DIR1-phospholipid crystal structure as template, provides clues as to why the dir1-1 mutant is rarely SAR-competent. The contribution of DIR1 and DIR1-like during SAR was examined using an Agrobacterium-mediated transient expression-SAR assay and an estrogen-inducible DIR1-EGFP/dir1-1 line. We provide evidence that upon SAR induction, DIR1 moves down the leaf petiole to distant leaves. Our data also suggests that DIR1-like displays a reduced capacity to move to distant leaves during SAR and this may explain why dir1-1 is occasionally SAR-competent.

Hardness methods for testing maize kernels

Maize is a highly important crop to many countries around the world, through the sale of the maize crop to domestic processors and subsequent production of maize products and also provides a staple food to subsistance farms in undeveloped countries. In many countries, there have been long-term research efforts to develop a suitable hardness method that could assist the maize industry in improving efficiency in processing as well as possibly providing a quality specification for maize growers, which could attract a premium. This paper focuses specifically on hardness and reviews a number of methodologies as well as important biochemical aspects of maize that contribute to maize hardness used internationally. Numerous foods are produced from maize, and hardness has been described as having an impact on food quality. However, the basis of hardness and measurement of hardness are very general and would apply to any use of maize from any country. From the published literature, it would appear that one of the simpler methods used to measure hardness is a grinding step followed by a sieving step, using multiple sieve sizes. This would allow the range in hardness within a sample as well as average particle size and/or coarse/fine ratio to be calculated. Any of these parameters could easily be used as reference values for the development of near-infrared (NIR) spectroscopy calibrations. The development of precise NIR calibrations will provide an excellent tool for breeders, handlers, and processors to deliver specific cultivars in the case of growers and bulk loads in the case of handlers, thereby ensuring the most efficient use of maize by domestic and international processors. This paper also considers previous research describing the biochemical aspects of maize that have been related to maize hardness. Both starch and protein affect hardness, with most research focusing on the storage proteins (zeins). Both the content and composition of the zein fractions affect hardness. Genotypes and growing environment influence the final protein and starch content and, to a lesser extent, composition. However, hardness is a highly heritable trait and, hence, when a desirable level of hardness is finally agreed upon, the breeders will quickly be able to produce material with the hardness levels required by the industry.

Role of plant lipid transfer proteins in plant cell physiology-a concise review

Plant lipid transfer proteins (LTP) are cationic peptides, subdivided into two families, which present molecular masses of around 7 and 10 kDa. The peptides were, thus, denominated due to their ability to reversibly bind and transport hydrophobic molecules in vitro. Both subfamilies possess conserved patterns of eight cysteine residues and the three-dimensional structure reveals an internal hydrophobic cavity that comprises the lipid binding site. Based on the growing knowledge regarding structure, gene expression and regulation and in vitro activity, LTPs are likely to play a role in key processes of plant physiology. Although the roles of plant LTPs have not yet been fully determined. This review aims to present comprehensive information of recent topics, cover new additional data, and present new perspectives on these families of peptides.