Lipid transfer proteins: classification, nomenclature, structure, and function

Salminen, Tiina A.; Blomqvist, Kristina; Edqvist, Johan

doi:10.1007/s00425-016-2585-4

Cited by 197 publications

(220 citation statements)

References 118 publications

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“…Ligand binding to LTPs is accompanied by slight changes in the unstructured C-terminal tail of the protein, which acts as a lid on the hydrophobic cavity, although the a-helical fold is preserved (Salcedo et al 2007;Salminen et al 2016). Consistent with the behaviour described for LTPs upon ligand binding, the presence of the ligand produced a distortion in the circular dichroism spectrum of Pru p 3 in the vacuum UV region (190-200 nm).…”

Section: Discussionsupporting

confidence: 58%

“…Despite the considerable heterogeneity in their primary structure, all LTPs share a compact a-helical fold composed of four a-helices connected by short loops and a non-structured C-terminal tail. This fold is stabilized by eight conserved cysteine residues that form four disulfide bonds (Pacios et al 2012;Salcedo et al 2007;Salminen et al 2016). A characteristic tunnel-like cavity aligned with the long axis of the protein is formed by the space left within the helices.…”

Section: Introductionmentioning

confidence: 99%

“…Hydrophobic side chains coat the inner surface of this cavity, which is large enough to accommodate ligands with long chains (Hamilton 2004;Sossountzov et al 1991;Zachowski et al 1998). These properties point to a potential role for LTPs in membrane biogenesis, and some members are thought to have a role in defence against pathogens (Molina and Garcia-Olmedo 1993), transport of cutin monomers, and fruit and flower development (Chae et al 2010;Salcedo et al 2007;Salminen et al 2016). The ability of plant nsLTPs to bind a wide variety of lipids enables them to perform various functions (Pacios et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Identification of the ligand of Pru p 3, a peach LTP

et al. 2017

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Key message Pru p 3, a peach LTP, is located in pollinated flower styles and secreting downy hairs, transporting a derivative of camptothecin bound to phytosphingosine. Pru p 3 may inhibit a second pollination and may keep away herbivores until seed maturation. Abstract The allergen Pru p 3, a peach lipid transfer protein, has been well studied. However, its physiological function remains to be elucidated. Our results showed that Pru p 3 usually carries a lipid ligand that play an essential role in its function in plants. Using ESI-qToF, we observed that the ligand was a derivative of camptothecin binding to phytosphingosine, wich that is inserted into the hydrophobic tunnel of the protein. In addition, the described ligand displayed topoisomerase I activity inhibition and self-fluorescence, both recognized as camptothecin properties. During flower development, the highest expression of Pru p 3 was detected in the styles of pollinated flowers, in contrast to its non-expression in unpollinated pistils, where expression decreased after anthesis. During ripening, the expression of Pru p 3 were observed mainly in peel but not in pulp. In this sense, Pru p 3 protein was also localized in trichomes covering the fruit epidermis.

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Section: Discussionsupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Identification of the ligand of Pru p 3, a peach LTP

et al. 2017

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“…Excretion of lipophilic compounds across the plasma membrane via ATP-binding cassette (ABC) transporters is summarized in [1]. For non membrane-associated processes, lipid transfer and acyl-CoA binding proteins, membrane contact sites, vesicle traffic, or acyl-exchange mechanisms, we point to recent reviews [7][8][9][10][11]. However, it is noteworthy, that for FA/lipid traffic in general most likely membrane contacts as well as tight cooperation between transport and biosynthesis steps are required.…”

Section: Introductionmentioning

confidence: 99%

Plant membrane-protein mediated intracellular traffic of fatty acids and acyl lipids

Li‐Beisson¹,

Neunzig²,

Lee³

et al. 2017

Current Opinion in Plant Biology

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In plants, de novo synthesis of fatty acids (FAs) occurs in plastids, whereas assembly and modification of acyl lipids is accomplished in the endoplasmic reticulum (ER) and plastids as well as in mitochondria. Subsequently, lipophilic compounds are distributed within the cell and delivered to their destination site. Thus, constant acyl-exchanges between subcellular compartments exist. These can occur via several modes of transport and plant membrane-intrinsic proteins for FA/lipid transfer have been shown to play an essential role in delivery and distribution. Lately, substantial progress has been made in identification and characterization of transport proteins for lipid compounds in plant organelle membranes. In this review, we focus on our current understanding of protein mediated lipid traffic between organelles of land plants.

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“…LTPs are expressed in all investigated land plants, but have not been detected in any other organisms (7). LTPs are encoded by large gene families in seed plants (2,(8)(9)(10)(11). In bryophytes and ferns the gene families are significantly smaller (7,12).…”

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confidence: 99%

Plant lipid transfer proteins: are we finally closing in on the roles of these enigmatic proteins?

Edqvist

Blomqvist

Nieuwland

et al. 2018

Journal of Lipid Research

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100

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The nonspecific lipid transfer proteins (LTPs) are small, compact proteins folded around a tunnel-like hydrophobic cavity, making them suitable for lipid binding and transport. LTPs are encoded by large gene families in all land plants, but they have not been identified in algae or any other organisms. Thus, LTPs are considered key proteins for plant survival on and colonization of land. LTPs are abundantly expressed in most plant tissues, both above and below ground. They are usually localized to extracellular spaces outside the plasma membrane. Although the in vivo functions of LTPs remain unclear, accumulating evidence suggests a role for LTPs in the transfer and deposition of monomers required for assembly of the water-proof lipid barriers-such as cutin and cuticular wax, suberin, and sporopolleninformed on many plant surfaces. Some LTPs may be involved in other processes, such as signaling during pathogen attacks. Here, we present the current status of LTP research with a focus on the role of these proteins in lipid barrier deposition and cell expansion. We suggest that LTPs facilitate extracellular transfer of barrier materials and adhesion between barriers and extracellular materials. A growing body of research may uncover the true role of LTPs in plants. Overview of plant non-specific lipid transfer proteinsThe plant non-specific lipid transfer proteins (LTPs) are abundant, secreted, soluble, cysteinerich and small proteins with a molecular size usually below 10 kDa (1, 2). In the LTPs four conserved disulfide bridges, formed by an eight-Cys motif (8CM) with the general form CXn-C-Xn-CC-Xn-CXC-Xn-C-Xn-C, stabilize the folding of four or five α-helices into a very compact 3D-structure (3, 4 and Fig. 1). The folding of the helices results in a central hydrophobic cleft suitable for the binding of hydrophobic ligands, such as fatty acids and other lipids (Fig. 2). The compact structure renders the LTPs very insensitive to heat and denaturing agents (5, 6). LTPs are expressed in all investigated land plants, but have not been detected in any other organisms (7). LTPs are encoded by large gene families in seed plants (2,(8)(9)(10)(11). In bryophytes and ferns the gene families are significantly smaller (7,12). LTPs are classified in five major types (LTP1, LTP2, LTPc, LTPd and LTPg) and four minor types (LTPe, LTPf, LTPh, LTPj and LTPk) (7). The classification is based on the spacing between the Cys residues in the 8CM, the polypeptide sequence identity and the position of evolutionary conserved introns. The classification also reflects post-translational modifications, e.g. LTPs with a GPI-anchor belong to LTPg. LTPd and LTPg are encoded in all land plants which suggests that these were possibly the first LTP types that evolved in land plants. The most well-studied LTP types in flowering plants LTP1 and LTP2 probably evolved later since these are not found in liverworts, mosses or other non-seed plants (7). The LTPs are translated with an N-terminal signal peptide that has a potential to localize th...

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Lipid transfer proteins: classification, nomenclature, structure, and function

Cited by 197 publications

References 118 publications

Identification of the ligand of Pru p 3, a peach LTP

Identification of the ligand of Pru p 3, a peach LTP

Plant membrane-protein mediated intracellular traffic of fatty acids and acyl lipids

Plant lipid transfer proteins: are we finally closing in on the roles of these enigmatic proteins?

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