Identification of the gene ( lgtG ) encoding the lipooligosaccharide β chain synthesizing glucosyl transferase from Neisseria gonorrhoeae

Identification of the gene (lgtG) encoding the lipooligosaccharide β chain synthesizing glucosyl transferase from Neisseria gonorrhoeae

^*Laboratory of Bacterial Pathogenesis and Immunology, The Rockefeller University, New York, NY 10021; ^†Laboratory for Mass Spectrometry, The Rockefeller University, 1230 York Avenue, New York, NY 10021; ^‡Maxwell Finland Laboratory for Infectious Diseases, Boston Medical Center, Boston, MA 02118; and ^¶Department of Microbiology, University of Maryland, College Park, MD 20742

Contributed by Emil C. Gotschlich

Abstract

The lipooligosaccharide from Neisseria gonorrhoeae (GC), consists of lipid A, an oligosaccharide core and three branches, α, β, and γ. We report the cloning of the gene (lgtG, lipooligosaccharide glycosyl transferase G) encoding the glucosyl transferase of GC that initiates the β chain which consists of a lactosyl moiety. This gene contains a homopolymeric tract of cytidine [poly(C)] and we demonstrate that changes in the number of Cs in poly(C) account for the variation of β chain expression in different GC strains. Biochemical analyses and mass spectrometry clearly attribute the reactivity of mAb 2C7 to the presence of the lactosyl β chain. In addition, we demonstrate that in the absence of the lactosyl group, a phosphoethanolamine is added to generate a new antigenic epitope as evidenced by the gain of reactivity to mAb 2-L1–8. These results show that, like the α chain, the β chain of lipooligosaccharide is subject to antigenic variation.

Footnotes

↵ § To whom reprint requests should be addressed. e-mail: ecg{at}rockvax.rockefeller.edu.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession no. AF076919).
ABBREVIATIONS:

lgtG,

lipooligosaccharide glycosyl transferase G;

GC,

Neisseria gonorrhoeae;

LOS,

lipooligosaccharide;

PEA,

phosphoethanolamine;

HPAE,

high pH anion exchange chromatography;

PAD,

pulse amperometric detection;

MALDI,

matrix-assisted laser desorption ionization;

ToF,

time-of-flight;

RBS,

ribosome-binding site