title: Discovery of a cardiolipin synthase utilizing phosphatidylethanolamine and phosphatidylglycerol as substrates.
abstract: Depending on growth phase and culture conditions, cardiolipin (CL) makes up 5-15% of the phospholipids in Escherichia coli with the remainder being primarily phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). In E. coli, the cls and ybhO genes (renamed clsA and clsB, respectively) each encode a CL synthase (Cls) that catalyzes the condensation of two PG molecules to form CL and glycerol. However, a ΔclsAB mutant still makes CL in the stationary phase, indicating the existence of additional Cls. We identified a third Cls encoded by ymdC (renamed clsC). ClsC has sequence homology with ClsA and ClsB, which all belong to the phospholipase D superfamily. The ΔclsABC mutant lacks detectible CL regardless of growth phase or growth conditions. CL can be restored to near wild-type levels in stationary phase in the triple mutant by expressing either clsA or clsB. Expression of clsC alone resulted in a low level of CL in the stationary phase, which increased to near wild-type levels by coexpression of its neighboring gene, ymdB. CL synthesis by all Cls is increased with increasing medium osmolarity during logarithmic growth and in stationary phase. However, only ClsA contributes detectible levels of CL at low osmolarity during logarithmic growth. Mutation of the putative catalytic motif of ClsC prevents CL formation. Unlike eukaryotic Cls (that use PG and CDP-diacylglycerol as substrates) or ClsA, the combined YmdB-ClsC used PE as the phosphatidyl donor to PG to form CL, which demonstrates a third and unique mode for CL synthesis.
authors.affiliation: Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Brandon K
authors.initials: BK
authors.lastname: Tan
authors.forename: Mikhail
authors.initials: M
authors.lastname: Bogdanov
authors.forename: Jinshi
authors.initials: J
authors.lastname: Zhao
authors.forename: William
authors.initials: W
authors.lastname: Dowhan
authors.forename: Christian R H
authors.initials: CR
authors.lastname: Raetz
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Guan
mesh_terms: D000595:Amino Acid Sequence; D002308:Cardiolipins / Q000378:metabolism; D002853:Chromatography, Liquid; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010715:Phosphatidylglycerols / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics / Q000378:metabolism*
chemical_list: D002308:Cardiolipins; D029968:Escherichia coli Proteins; D007527:Isoenzymes; D008565:Membrane Proteins; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; C483858:phosphatidylethanolamine; D017855:Transferases (Other Substituted Phosphate Groups); C100091:cardiolipin synthetase