Functional analysis of a lipid galactosyltransferase synthesizing the major envelope lipid in the Lyme disease spirochete Borrelia burgdorferi.

• One of the major lipids in the membranes of Borrelia burgdorferi ismonogalactosyl diacylglycerol (MGalDAG), a glycolipid recently shown to carryantigenic potency. Herein, it is shown that the gene mgs (TIGR designationbb0454) of B. burgdorferi encodes for the protein bbMGS that, when expressed inEscherichia coli, catalyzes the glycosylation of 1,2-diacylglycerol withspecificity for the donor substrate UDP-Gal yielding MGalDAG. Related lipidenzymes were found in many Gram-positive bacteria. The presence of thisgalactosyltransferase activity and synthesis of a cholesteryl galactoside byanother enzyme were verified in B. burgdorferi cell extract. Besides MGalDAG,phosphatidylcholine, phosphatidylglycerol, and cholesterol were also found asmajor lipids in the cell envelope. The high isoelectric point of bbMGS andclustered basic residues in its amino acid sequence suggest that the enzymeinteracts with acidic lipids in the plasma membrane, in agreement with strongenzymatic activation of bbMGS by phosphatidylglycerol. The membrane packing andimmunological properties of MGalDAG are likely to be of great importance in vivo.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Cell- och molekylärbiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Cell and Molecular Biology (hsv//eng)

Keyword

Bacterial Proteins/genetics/*metabolism

Borrelia burgdorferi/*enzymology/genetics

Cell Membrane/chemistry

Cholesterol/analysis/isolation & purification

Cloning; Molecular

Diglycerides/*biosynthesis/metabolism

Enzyme Activators/analysis/isolation & purification/pharmacology

Escherichia coli/genetics/metabolism

Galactolipids/*metabolism

Galactosyltransferases/genetics/*metabolism

Genes; Bacterial

Isoelectric Point

Lipid Metabolism

Membrane Lipids/*biosynthesis

Phosphatidylcholines/analysis/isolation & purification

Phosphatidylglycerols/analysis/isolation & purification/pharmacology

Recombinant Proteins/genetics/metabolism

Sequence Analysis; Protein

Transcription; Genetic

Uridine Diphosphate Galactose/metabolism

Publication and Content Type

vet (subject category)

art (subject category)