摘要
The authors have isolated and characterized a novel serine palmitoyltransferase （SPT）-like gene in marine Emiliania huxleyi virus （EhV-99B1）. The open-reading frame （ORF） of EhV99BI-SPT encoded a protein of 496 amino acids with a calculated molecular mass of 96 kDa and Ip 6.01. The results of sequence analysis showed that there was about 31% 45% identity in amino acid sequence with other organisms. The maximum likelihood phylogenetic tree suggested that the EhV99B1-SPT gene possibly horizontally transferred from the eukaryote. Hydrophobic profiles of deduced amino acid sequences suggested a hydrophobic, globular and membrane-associated protein with five transmembrane domains （TMDs） motifs. Several potential N-linked glycosylation sites were presented in SPT. These results suggested that EhV99BI-SPT was an integral endoplasmic reticulum membrane protein. Despite lower sequence identity, the secondary and three-dimensional structures predicted showed that the “pocket” structure element composed of 2a-helices and 4β- sheets was the catalytic center of this enzyme, with a typical conserved “TFTKSFG” active site in the N-terminal region and was very close to those of prokaryotic organisms. However, the N-terminal domain of EhV99B1-SPT most closely resembled the LCB2 catalysis subunit and the C-terminal domain most closely resembled the LCBI regulatory subunit of other organisms which together formed a spherical molecule. This “chimera” was highly similar to the prokaryotic homologous SPT. For a functional identification, the EhV99B1-LCB2 subunit gene was expressed in Escherichia coli, which resulted in significant accumulation of new sphingolipid in E. coli cells.
The authors have isolated and characterized a novel serine palmitoyltransferase （SPT）-like gene in marine Emiliania huxleyi virus （EhV-99B1）. The open-reading frame （ORF） of EhV99BI-SPT encoded a protein of 496 amino acids with a calculated molecular mass of 96 kDa and Ip 6.01. The results of sequence analysis showed that there was about 31% 45% identity in amino acid sequence with other organisms. The maximum likelihood phylogenetic tree suggested that the EhV99B1-SPT gene possibly horizontally transferred from the eukaryote. Hydrophobic profiles of deduced amino acid sequences suggested a hydrophobic, globular and membrane-associated protein with five transmembrane domains （TMDs） motifs. Several potential N-linked glycosylation sites were presented in SPT. These results suggested that EhV99BI-SPT was an integral endoplasmic reticulum membrane protein. Despite lower sequence identity, the secondary and three-dimensional structures predicted showed that the “pocket” structure element composed of 2a-helices and 4β- sheets was the catalytic center of this enzyme, with a typical conserved “TFTKSFG” active site in the N-terminal region and was very close to those of prokaryotic organisms. However, the N-terminal domain of EhV99B1-SPT most closely resembled the LCB2 catalysis subunit and the C-terminal domain most closely resembled the LCBI regulatory subunit of other organisms which together formed a spherical molecule. This “chimera” was highly similar to the prokaryotic homologous SPT. For a functional identification, the EhV99B1-LCB2 subunit gene was expressed in Escherichia coli, which resulted in significant accumulation of new sphingolipid in E. coli cells.
基金
The National High Technology Research and Development Program of China under contract No. 2008AA09Z408
Fujian Province Nature Science Foundation,China under contract No. 2010J01261
the Foundation for Innovative Research Team of Jimei University,China under contract No. 2010A007
