Reference "Barley lipid-transfer protein complexed with palmitoyl CoA: the structure reveals a hydrophobic binding site that can expand to fit both large and small lipid-like ligands"

Reference ID

8709

Title

Barley lipid-transfer protein complexed with palmitoyl CoA: the structure reveals a hydrophobic binding site that can expand to fit both large and small lipid-like ligands

Source

Structure (London, England), 1997, vol. 5, pp. 291-306

Authors (4)

Lerche-M-H	Kragelund-B-B
Bech-L-M	Poulsen-F-M

Abstract

BACKGROUND:. Plant nonspecific lipid-transfer proteins (nsLTPs) bind a variety
of very different lipids in vitro, including phospholipids, glycolipids, fatty
acids and acyl coenzyme As. In this study we have determined the structure of a
nsLTP complexed with palmitoyl coenzyme A (PCoA) in order to further our
understanding of the structural mechanism of the broad specificity of these
proteins and its relation to the function of nsLTPs in vivo. RESULTS:. 1H and
13C nuclear magnetic resonance spectroscopy (NMR) have been used to study the
complex between a nsLTP isolated from barley seeds (bLTP) and the ligand PCoA.
The resonances of 97% of the 1H atoms were assigned for the complexed bLTP and
nearly all of the resonances were assigned in the bound PCoA ligand. The
palmitoyl chain of the ligand was uniformly 13C-labelled allowing the two ends
of the hydrocarbon chain to be assigned. The comparison of a subset of 20
calculated structures to an average structure showed root mean square deviations
of 1.89 +/- 0.19 for all C, N, O, P and S atoms of the entire complex and of
0.57 +/- 0.09 for the peptide backbone atoms of the four alpha helices of the
complexed bLTP. The four-helix topology of the uncomplexed bLTP is maintained in
the complexed form of the protein. The bLTP only binds the hydrophobic parts of
PCoA with the rest of the ligand remaining exposed to the solvent. The palmitoyl
chain moiety of the ligand is placed in the interior of the protein and bent in
a U-shape. This part of the ligand is completely buried within a hydrophobic
pocket of the protein. CONCLUSIONS:. A comparison of the structures of bLTP in
the free and bound forms suggests that bLTP can accommodate long olefinic
ligands by expansion of the hydrophobic binding site. This expansion is achieved
by a bend of one helix, HA, and by conformational changes in both the C terminus
and helix HC. This mode of binding is different from that seen in the structure
of maize nsLTP in complex with palmitic acid, where binding of the ligand is not
associated with structural changes.