Purification of a phosphatidylinositol/phosphatidylcholine transfer protein from Neurospora crassa

Increased phospholipid transfer protein activity in Aspergillus oryzae grown on various industrial phospholipid sources

The effect of industrial carbon sources on phospholipid transfer protein production was investigated. Phospholipid fractions of different composition were prepared from various plant oils (i.e., soybean, rapeseed, and sunflower) according to the Lucas Meyer extraction and purification process. The effect of these fractions on phospholipid transfer protein activity of cell extracts from Aspergillus oryzae grown on medium containing these phospholipids as sole carbon source was studied. It was shown that phospholipid transfer activity was markedly increased by extracts containing a particular phospholipid composition. However, this stimulation depends mainly upon the phospholipid composition of the fraction used as fermentation substrate. Fractions enriched mainly in phosphatidylinositol (Epikuron 110), at the expense of phosphatidylcholine, were the most efficient sources for phospholipid transfer protein production by A. oryzae. Maximal phospholipid transfer activity, as well as biomass production, were increased 4.1- and 9.7-fold, respectively, when cultures were supplemented with Epikuron 110 prepared from sunflower lecithin, as compared to glucose-control cultures.

Cloning and expression in phospholipid containing cultures of the gene encoding the specific phosphatidylglycerol/phosphatidylinositol transfer protein from Aspergillus oryzae: evidence that the pg/pi-tp is tandemly arranged with the putative 3-ketoacyl-CoA thiolase gene

The phosphatidylglycerol/phosphatidylinositol transfer protein (PG/PI-TP) is a new and original phospholipid transfer protein (PLTP) isolated from the Deuteromycete, Aspergillus oryzae. We have isolated a genomic clone of the A. oryzae pg/pi-tp using a probe derived from the corresponding cDNA and sequenced the complete gene. The DNA sequence analysis revealed that pg/pi-tp gene is composed of three exons encoding a 18,823 Da protein of 175 amino acids as previously described and of two introns as deduced by cDNA and genomic sequence alignment. The isolated pg/pi-tp gene do not show similarity with other PLTP genes or the deduced PG/PI-TP protein with proteins already known. Comparison of the encoded PG/PI-TP with other deduced proteins from recent genomic or cDNA sequence from databases revealed that the PG/PI-TP was close to two encoded proteins deduced from the cDNA database of Aspergillus nidulans (54% identity and 68% similarity) and the second from Neurospora crassa (53% identity and 76% similarity). Therefore, we suggested that both proteins might belong to the PLTP family. Southern blot analysis of A. oryzae genomic DNA show that the PG/PI-TP was encoded by a single gene. Expression of pg/pi-tp was performed in phospholipid containing cultures with increasing carbon source concentrations in order to study the regulation of the PLTPs in the filamentous fungus cell. This was done to know if a high density culture could yield a high amount of biomass with high phospholipid transfer activity. Results showed that phospholipids as compared to glucose in standard cultures stimulated mycelial growth and global phospholipid transfer activity, but not the pg/pi-tp transcript accumulation. However, high concentration of both carbon sources yielded an inhibition of the expression of the pg/pi-tp gene and of the global phospholipid transfer activity. In conclusion, both carbon sources are not suitable to increase the PLTP production in high density cultures for biotechnological applications. Finally, using the gene walking sequencing method it is demonstrated that the pg/pi-tp is tandemly arranged on opposite DNA strands in a tail-to-tail orientation with a putative gene encoding the 3-ketoacyl-CoA thiolase (EC 2.3.1.16). Unlike the pg/pi-tp gene, this thiolase gene show a putative 'beta-oxidation box' and encodes a putative 44,150 Da protein of 321 amino acids composed of a putative N-terminal PTS2 (Peroxisomal Targeting Signal) consensus sequence for the peroxisome targeting. Comparison of the amino acid sequence of the A. oryzae thiolase to that of the Yarrowia lipolytica showed a 50% identity and a 69% similarity.

Phosphatidylinositol transfer proteins: requirements in phospholipase C signaling and in regulated exocytosis

Phosphatidylinositol transfer proteins (PITP) are abundant cytosolic proteins originally identified because of their ability to act in vitro as specific transporters of phosphatidylinositol or phosphatidylcholine between membranes. However, the cellular function of mammalian PITP has remained enigmatic till recently. Due to the development of reconstitution assays in cytosol-depleted cells, PITP was found to be an essential component for phospholipase C-mediated hydrolysis of PIP2 and for regulated exocytosis. The exact mechanism how PITP exerts its effects is not known but the PI binding/transfer activity of PITP can partly explain its cellular function. PITP would enable the local synthesis of PIP2 by delivering PI to specialized signaling sites.

Purification and characterization of a novel specific phosphatidylglycerol-phosphatidylinositol transfer protein with high activity from Aspergillus oryzae

A novel phospholipid transfer protein has been purified to homogeneity 406-fold from the filamentous fungus Aspergillus oryzae. The successive steps of purification comprised ultrafiltration, gel filtration on Sephadex G-75, ion exchange chromatographies on DEAE-Sepharose and Mono Q. The active protein is a monomer with a molecular mass of 19,000, estimated from SDS electrophoresis, amino acid composition as well as gel filtration. The isoelectric point is 4.8. The amino acid composition is characterized by a high amount of Gly, Leu, Ser, Asx and Glx residues and 4 Cys residues. N-terminal sequence was determined and compared with M. mucedo sequence. The purified protein was found to transfer preferentially phosphatidylglycerol and phosphatidylinositol over phosphatidylcholine > phosphatidylethanolamine > phosphatidylserine and no phosphatidic acid. Optimal temperature for in vitro transfer was 25-30 degrees C and optimal pH 4-7. Heating protein at 100 degrees C does not inactivate protein whereas a denaturation with urea is irreversible.

Filamentous Fungi with High Cytosolic Phospholipid Transfer Activity in the Presence of Exogenous Phospholipid

The phospholipid transfer activity of cell extracts from 15 filamentous fungus strains grown on a medium containing phospholipids as the carbon source was measured by a fluorescence assay. This assay was based on the transfer of pyrene-labeled phosphatidylcholines forming the donor vesicles to acceptor vesicles composed of egg phosphatidylcholines. The highest phosphatidylcholine transfer activity was obtained with cell extracts from Aspergillus oryzae . The presence of exogenous phospholipids in the culture medium of A. oryzae was shown to increase markedly the activity of phospholipid transfer as well as the pool of exocellular proteins during the primary phase of growth. Modifications in the biochemical marker activities of cellular organelles were observed: succinate dehydrogenase, a mitochondrial marker; inosine diphosphatase, a Golgi system marker; and cytochrome c oxidoreductase, an endoplasmic reticulum marker, were increased 7.3-, 2-, and 22-fold, respectively, when A. oryzae was grown in the presence of phospholipids.

Interaction of phospholipids with proteins and peptides. New advances IV

1. The review deals with the newest achievements in the field of the various interactions between phospholipids and proteins and peptides. 2. Interactions are classified according to the hydrophobic, hydrophilic or mixed character of the interactive forces. 3. The effect of the interaction on the structure and biological activity of the interacting molecular assemblies is also discussed.