The enzyme was purified to about 90 percent homogeneity from an overproducing strain, its amino-acid composition matching the product of the cloned cds gene, and it required a different detergent at each purification step.

Purified enzyme shows surface-dilution kinetics in Triton X-100 and a sequential rather than ping-pong mechanism, with kinetic constants reported.

The hydrophobic, detergent-dependent behaviour of the protein through every purification step is consistent with an integral membrane protein.

The activity was solubilised from the cell envelope with digitonin and purified about 70-fold, establishing a membrane location biochemically.

One enzyme makes both CDP-diglyceride and dCDP-diglyceride, CTP and dCTP being competitive substrates, so the single GO term covers both products.

The enzyme also catalyses the reverse pyrophosphorolysis in vitro; UniProt records the physiological direction as phosphatidic acid to CDP-diacylglycerol, so this is not a second function.

Conditionally lethal cds mutants accumulate phosphatidic acid to about 30 percent of membrane lipid above pH 8 while phosphatidylethanolamine and phosphatidylglycerol synthesis is inhibited more than ten-fold, and the liponucleotide pool falls to about a seventh of wild type.

The authors conclude that CDP-diglyceride is an obligatory precursor of more than 90 percent of the two major E. coli phospholipids, which is the in vivo basis for treating this reaction as the committed step.

C-terminal alkaline phosphatase and GFP tagging fixed the periplasmic or cytoplasmic location of the C-terminus for 601 inner membrane proteins, and those constraints were used to derive topology models.

Depleting CdsA leaves MPIase undetectable and blocks M13 procoat processing, while overproducing CdsA raises MPIase about three-fold.

Inverted vesicles from CdsA overproducers and partially purified CdsA8 convert labelled phosphatidic acid, CTP and GlcNAc-1-phosphate into the first MPIase intermediate, identified against a synthetic reference by chromatography and mass spectrometry, with CDP-diacylglycerol apparently not released from the enzyme.

cdsA is essential; neither the knockout nor the cdsA ynbB double knockout grows without induction of the complementing plasmid.

Under CdsA depletion, YnbB overproduction restores MPIase but not phospholipid synthesis, and chimera analysis attributes the fast CDP-diacylglycerol synthesis needed for growth to the N-terminal half of CdsA.

The authors read YnbB as a backup dedicated to the MPIase branch, which leaves the division of labour between the two paralogues in the wild type unresolved.

MPIase rises in the cold and the rise depends on cdsA or ynbB, which the authors describe as rate-limiting enzymes for MPIase biosynthesis.

MPIase is the glycolipid that drives membrane protein integration into the E. coli cytoplasmic membrane, which is the entity that acts on the substrate protein, not CdsA.

Curated catalytic activity with Rhea 16229 and the physiological direction, pathway position, inner membrane location, essentiality and MPIase involvement, each tied to the primary literature by ECO:0000269.

The entry places the enzyme at the final step of CDP-diacylglycerol biosynthesis from sn-glycerol 3-phosphate.

The gene cannot be deleted, and depletion causes a phospholipid-synthesis defect together with MPIase loss and accumulation of membrane and secretory protein precursors.

Family placement is supported by independent signature resources, the CDS family note, the NCBIfam model for cdsA, Pfam CTP_transf_1 and PROSITE PS01315.

P0ABG1 is listed as a member of PTHR46382 and of its single subfamily SF1, alongside bacterial orthologues from B. subtilis, Aquifex and Chlamydia, which confirms the family placement the IBA rows depend on without relying on the GOA row itself.