Acyl carrier proteins from sunflower (Helianthus annuus L.) seeds and their influence on FatA and FatB acyl-ACP thioesterase activities

• Published in: Planta Vol. 244; no. 2; pp. 479 - 490
• Main Authors: Aznar-Moreno, Jose A., Venegas-Calerón, Mónica, Martínez-Force, Enrique, Garcés, Rafael, Salas, Joaquín J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Science + Business Media 01.08.2016; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Agriculture; Biomedical and Life Sciences; Cloning; Cloning, Molecular; Ecology; Fatty acids; Fatty Acids - biosynthesis; Forestry; Helianthus; Helianthus - genetics; Helianthus - metabolism; Helianthus annuus; Life Sciences; Lipid Metabolism; ORIGINAL ARTICLE; Phylogeny; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Sciences; Protein Domains; Proteins; Seeds; Seeds - genetics; Seeds - metabolism; Sequence Alignment; Sequence Analysis, Protein; Substrate Specificity; Sunflower oil; Thiolester Hydrolases - metabolism; Acyl-ACP thioesterase; Sunflower; Acyl carrier protein; Fatty acid synthesis; Sunflower, Helianthus annuus
• DOI: 10.1007/s00425-016-2521-7
• ISSN: 0032-0935

Acyl carrier proteins (ACPs) are small (~ 9 kDa), soluble, acidic proteins involved in fatty acid synthesis in plants and bacteria. ACPs bind to fatty acids through a thioester bond, generating the acyl-ACP lipoproteins that are substrates for fatty acid synthase (FAS) complexes, and that are required for fatty acid chain elongation, acting as important intermediates in de novo fatty acid synthesis in plants. Plants, usually express several ACP isoforms with distinct functionalities. We report here the cloning of three ACPs from developing sunflower seeds: HaACP1, HaACP2, and HaACP3. These proteins were plastidial ACPs expressed strongly in seeds, and as such they are probably involved in the synthesis of sunflower oil. The recombinant sunflower ACPs were expressed in bacteria but they were lethal to the prokaryote host. Thus, they were finally produced using the GST gene fusion system, which allowed the apo-enzyme to be produced and later activated to the holo form. Radio-labelled acyl-ACPs from the newly cloned holo-ACP forms were also synthesized and used to characterize the activity of recombinant sunflower FatA and FatB thioesterases, important enzymes in plant fatty acids synthesis. The activity of these enzymes changed significantly when the endogenous ACPs were used. Thus, FatA importantly increased its activity levels, whereas FatB displayed a different specificity profile, with much high activity levels towards saturated acyl-CoA derivatives. All these data pointed to an important influence of the ACP moieties on the activity of enzymes involved in lipid synthesis.