Homology modelling and molecular dynamics aided analysis of ligand complexes demonstrates functional properties of lipid‐transfer proteins encoded by the barley low‐temperature‐inducible gene family, blt4

Abstract

SummaryThe homology modelling technique was used to predict the tertiary structures of three members of the lowtemperature-inducible barley vegetative shoot epidermal lipid-transfer protein (LTP) family, BLT4, on the basis of the X-ray crystallographically determined three-dimensional structure of a maize seedling LTP. Differences between the maize LTP and the BLT4 family include amino acid substitutions around the entrance and inside the predicted hydrophobic binding tunnels of these proteins. Because of the deletion of the loop region corresponding to Val60-Gly62 of the maize LTP from all three BLT4 LTPs, their internal hydrophobic tunnels are longer. Molecular dynamics modelling shows that BLT4.9 can accommodate hexadecanoic acid in its binding tunnel in similar conformation to the maize LTP. However, modelled cis,cis-9,12-octadecandienoic acid had a more favourable interaction with the BLT4.9 LTP than with the maize protein. Di-cis,cis-9,12-octadecandienoyl phosphatidylglycerol and di-cis,cis-9,12-octadecandienoyl phosphatidylcholine were modelled in the BLT4.9 structure with the fatty acyl group at position 1 embedded in the binding tunnel and the group at position 2 located on the solvent accessible surface of the protein. The results of the modelling suggest that the phospholipid headgroup can form hydrogen and salt bridges with polar and charged residues outside the binding tunnel and the exposed hydrocarbon chain interacts with hydrophobic amino acids on the surface. These results are consistent with the proposal that BLT4 LTPs have a lipid-transfer function associated with frost acclimation in barley.

Cold induced expression of plant defensin and lipid transfer protein transcripts in winter wheat

“…Five different LTP groups were apparent based on sequence similarity; all groups exhibited high homology to different families of barley non‐specific LTPs, recently associated with defence responses in plants (García‐Olmedo et al 1998). The blt4.9 gene in barley, homologous to clone TaLt19C10 in this study, was previously identified as low‐temperature‐responsive (Hughes et al 1992, White et al 1994, Keresztessy and Hughes 1998). LTPs in winter wheat appear to be members of a multigene family that are upregulated in a similar fashion in response to exposure to above‐zero, hardening temperatures.…”

Comparison of Lipid Binding and Transfer Properties of Two Lipid Transfer Proteins from Plants

“…Knowledge of the relationship between the cavity structure and the affinity for various lipidic ligands, as well as between protein structure and membrane interaction, would help in defining the role(s) of the various isoforms of LTP. As an example, it was shown that a lowtemperature-inducible barley LTP differs in its structural and functional properties from maize LTP (49). This could be related to potential roles of LTP in frost acclimatization in plants.…”

The eight-cysteine motif, a versatile structure in plant proteins

“…Results show that only one acyl chain of the hydrophobic tails of fatty acids is inserted in the protein internal cavity. Different conformational changes are observed after lipid binding to the different LTPs as a consequence of their different cavity size and accessibility [40,44,63,65]. A limit example of variability in the internal cavity is given by Ace-AMP1, a potent antimicrobial LTPlike protein described in onion seeds [69] and that has two tryptophan residues in its primary sequence.…”