Comparison of solution and crystal structures of maize nonspecific lipid transfer protein: A model for a potential in vivo lipid carrier protein

Abstract

The three-dimensional solution structure of maize nonspecific lipid transfer protein (nsLTP) obtained by nuclear magnetic resonance (NMR) is compared to the X-ray structure. Although both structures are very similar, some local structural differences are observed in the first and the fourth helices and in several side-chain conformations. These discrepancies arise partly from intermolecular contacts in the crystal lattice. The main characteristic of nsLTP structures is the presence of an internal hydrophobic cavity whose volume was found to vary from 237 to 513 A3 without major variations in the 15 solution structures. Comparison of crystal and NMR structures shows the existence of another small hollow at the periphery of the protein containing a water molecule in the X-ray structure, which could play an important structural role. A model of the complexed form of maize nsLTP by alpha-lysopalmitoylphosphatidylcholine was built by docking the lipid inside the protein cavity of the NMR structure. The main structural feature is a hydrogen bond found also in the X-ray structure of the complex maize nsLTP/palmitate between the hydroxyl of Tyr81 and the carbonyl of the lipid. Comparison of 12 primary sequences of nsLTPs emphasizes that all residues delineating the cavities calculated on solution and X-ray structures are conserved, which suggests that this large cavity is a common feature of all compared plant nsLTPs. Furthermore several conserved basic residues seem to be involved in the stabilization of the protein architecture.

1H NMR and fluorescence studies of the complexation of DMPG by wheat non‐specific lipid transfer protein. Global fold of the complex

“…A thorough analysis of the dimensions of the protein cavity showed that the volume is highly variable depending on small conformational changes of internal side-chains and backbone [21]. The present study shows that ns-LTPs are able to interact with both monoacyl and diacyl lipids and with both lipid forming micelles or lamellar liquid-crystalline phases.…”

“…The volume of the internal hydrophobic cavity occupied by the two myristoyl chains was estimated to be 750 A 3 (±250 A 3 ) using the program 'CAVITE' [21]. The pocket was bordered by hydrophobic residues belonging to the four helices and to the C-terminal tail.…”

“…The best DIANA structure was used to build a preliminary structure of the complex with DMPG via the SYBYL software (Tripos, St. Louis, MO, USA) on a SILICON GRAPHICS workstation as follows : the use of the program 'CAVITE', which delineates cavity inside protein structures [21], defined a large hydrophobic cavity in the interior of the DIANA structure where both chains of the lipid were inserted. The orientation of the lipid was deduced from intermolecular NOEs between the lipid glycerol moieties and side-chain protons of residues His 35 and Arg 44 .…”

Two SCA (Stigma/Style Cysteine-rich Adhesin) Isoforms Show Structural Differences That Correlate with Their Levels of in Vitro Pollen Tube Adhesion Activity

“…In previous studies of the maize LTP-long chain lipid complex, a hydrogen bond was found between the carboxylate or carbonyl group of the lipid and the hydroxyl of the C-terminal Tyr 81 (in maize LTP numbering), stabilizing the protein-lipid complex (11,12,58). The conserved N-terminal Tyr 17 (in maize LTP numbering) on the helix H1 is mostly solvent-exposed (12), and its role in the lipid complexation is obscure.…”

Isolation and characterization of a lipid transfer protein expressed in ripening fruit of Capsicum chinense

“…Three-dimensional structures of LTPs from maize (Gomar et al 1996(Gomar et al , 1998, wheat (Pons et al 2003) and barley (Lerche and Poulsen 1998) have led to a model structure of four helices linked by three loops and a C-terminal tail without a regular structure (Han et al 2001;Stolowich et al 1997). A fold is established by the four disulfide bonds and the helices encode an internal K.…”