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Enzymatic properties and substrate specificity of a bacterial phosphatidylcholine synthase
Author(s) -
Aktas Meriyem,
Köster Stefan,
Kizilirmak Sarah,
Casanova Javier C.,
Betz Heidi,
Fritz Christiane,
Moser Roman,
Yildiz Özkan,
Narberhaus Franz
Publication year - 2014
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12877
Subject(s) - biochemistry , enzyme , cytidine , chemistry , atp synthase , biology
Phosphatidylcholine ( PC ) is a rare membrane lipid in bacteria, but is crucial for virulence of the plant pathogen A grobacterium tumefaciens and various other pathogens. Agrobacterium tumefaciens uses two independent PC biosynthesis pathways. One is dependent on the integral membrane protein PC synthase (Pcs), which catalyzes the conversion of cytidine diphosphate–diacylglycerol ( CDP – DAG ) and choline to PC , thereby releasing a cytidine monophosphate ( CMP ). Here, we show that Pcs consists of eight transmembrane segments with its N‐ and C‐termini located in the cytoplasm. A cytoplasmic loop between the second and third membrane helix contains the majority of the conserved amino acids of a CDP ‐alcohol phosphotransferase motif ( DGX 2 ARX 12 GX 3 DX 3 D). Using point mutagenesis, we provide evidence for a crucial role of this motif in choline binding and enzyme activity. To study the catalytic features of the enzyme, we established a purification protocol for recombinant Pcs. The enzyme forms stable oligomers and exhibits broad substrate specificity towards choline derivatives. The presence of CDP – DAG and manganese is a prerequisite for cooperative binding of choline. PC formation by Pcs is reversible and proceeds via two successive reactions. In a first choline‐ and manganese‐independent reaction, CDP – DAG is hydrolyzed releasing a CMP molecule. The resulting phosphatidyl intermediate reacts with choline in a second manganese‐dependent step to form PC . Structured digital abstractPcs and Pcs bind by molecular sieving ( 1 , 2 , 3 )