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

Abstract

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.

The Long-Distance Transport of Some Plant Hormones and Possible Involvement of Lipid-Binding and Transfer Proteins in Hormonal Transport

“…Here, we would like to discuss another mechanism possibly implicated in the long-distance transport of hormones, which involves Lipid-Binding and Transfer Proteins (LBTPs). It is assumed that proteins of this type provide the necessary solubility of hydrophobic substances in the hydrophilic spaces and enable their movement throughout the plants [ 72 ]. Since ABA, cytokinin bases, JA, and several other hormones are considered lipophilic [ 73 ], it is not surprising that the ability of LBTPs to bind these hormones has been found and reported in several articles [ 74 , 75 , 76 , 77 ].…”

“…Plant Lipid-Binding and Transfer Proteins include several classes of proteins, of which pathogenesis-related proteins class 10 (PR-10) and 14, also known as lipid transfer proteins (LTPs), are capable of binding plant hormones [ 72 , 74 ]. They are characterized by the presence of a hydrophobic cavity, inside which the ligand-binding site is located [ 72 ]. These proteins are able to reversibly bind various hydrophobic molecules of different chemical structures, including plant hormones such as JA, ABA, and cytokinins.…”

“…LTPs are capable of binding jasmonic acid [ 72 ], while jasmonic acid, as well as representatives of the LTP class, were found in the phloem sap of various plants [ 106 , 107 ] ( Table 1 and Figure 1 ). As mentioned above, jasmonates [ 108 ] and DIR1 [ 99 , 109 ] can participate in long-distance signaling during systemic acquired resistance (SAR).…”

“…Abscisic acid is one of the hormones that has been shown to be a ligand for LTPs [ 72 ]. However, the importance of LTPs for long-distance transport of ABA has received even less attention than the importance of these proteins for the systemic signaling of jasmonates.…”

“…This complex is transported from shoots to roots. PR-10 of Vigna radiata in complex with zeatin (PDB 2FLH) and LTP of Pisum sativum , capable of binding JA and ABA (PDB 2N81), are shown [ 72 , 77 ].…”