Fkn. Lee et al., Relationship between UDP-glucose 4-epimerase activity and oligoglucose glycoforms in two strains of Neisseria meningitidis, INFEC IMMUN, 67(3), 1999, pp. 1405-1414
Sodium dodecyl sulfate-polyacrylamide gel analysis of lipooligosaccharide (
LOS) from Neisseria meningitidis has demonstrated considerable microheterog
eneity in the variable region of LOS due to the presence of novel glycoform
s, As a step toward understanding the basis for the expression of these nov
el glycoforms, we have examined the LOS structures and UDP-glucose 4-epimer
ase (epimerase) activity levels in two strains (NMB and MA-1) and their res
pective galE mutants. Strain NMB was found to have low epimerase activity a
nd to contain multiple glycoforms, some of which appear to contain only glu
cose sugars. The galE mutant had only the oligoglucose glycoforms, Strain M
A-1 had higher epimerase activity at both log and stationary phases (2- and
12.5-fold, respectively) and one glycoform with a putative lactosyl struct
ure. Strain MA-1 galE had two glycoforms that contained one or two glucose
residues. To understand I:he molecular basis for the different epimerase ac
tivities, we examined the predicted amino acid sequences of the respective
galE open reading frames and determined the relative amounts of GalE protei
n. We found no significant differences between the predicted amino acid seq
uence of the GalE protein in NMB and that in MA-1, We observed no significa
nt differences in the level of GalE protein between MA-1 and NMB at exponen
tial or stationary phase. We also observed an 8.2-fold drop in epimerase ac
tivity in NMB between the log and stationary phases that was not due to the
GalE protein level or low glucose levels.