title: A CDP-choline pathway for phosphatidylcholine biosynthesis in Treponema denticola.
abstract: The genomes of Treponema denticola and Treponema pallidum contain a gene, licCA, which is predicted to encode a fusion protein containing choline kinase and CTP:phosphocholine cytidylyltransferase activities. Because both organisms have been reported to contain phosphatidylcholine, this raises the possibility that they use a CDP-choline pathway for the biosynthesis of phosphatidylcholine. This report shows that phosphatidylcholine is a major phospholipid in T. denticola, accounting for 35-40% of total phospholipid. This organism readily incorporated [14C]choline into phosphatidylcholine, indicating the presence of a choline-dependent biosynthetic pathway. The licCA gene was cloned, and recombinant LicCA had choline kinase and CTP:phosphocholine cytidylyltransferase activity. The licCA gene was disrupted in T. denticola by erythromycin cassette mutagenesis, resulting in a viable mutant. This disruption completely blocked incorporation of either [14C]choline or 32Pi into phosphatidylcholine. The rate of production of another phospholipid in T. denticola, phosphatidylethanolamine, was elevated considerably in the licCA mutant, suggesting that the elevated level of this lipid compensated for the loss of phosphatidylcholine in the membranes. Thus it appears that T. denticola does contain a licCA-dependent CDP-choline pathway for phosphatidylcholine biosynthesis.
authors.affiliation: Department of Biological Chemistry, Medical School, University of Michigan, Ann Arbor, MI 48109-1078, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Kent
authors.forename: Patricia
authors.initials: P
authors.lastname: Gee
authors.forename: Si Young
authors.initials: SY
authors.lastname: Lee
authors.forename: Xuelin
authors.initials: X
authors.lastname: Bian
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Fenno
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002797:Choline Kinase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019916:Choline-Phosphate Cytidylyltransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003566:Cytidine Diphosphate Choline / Q000378:metabolism*; D017931:DNA Primers; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D010957:Plasmids / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014208:Treponema / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D014210:Treponema pallidum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D010713:Phosphatidylcholines; D011993:Recombinant Fusion Proteins; D003566:Cytidine Diphosphate Choline; D002797:Choline Kinase; D019916:Choline-Phosphate Cytidylyltransferase