MEMBRANE GLYCEROPHOSPHOLIPID BIOSYNTHESIS IN NEISSERIA-MENINGITIDIS AND NEISSERIA-GONORRHOEAE - IDENTIFICATION, CHARACTERIZATION, AND MUTAGENESIS OF A LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE

Lysophosphatidic acid (LPA) acyltransferases of Neisseria meningitidis and Neisseria gonorrhoeae were identified which share homology with o ther prokaryotic and eukaryotic LPA acyltransferases, In Escherichia c oil, the conversion of LPA to phosphatidic acid, performed by the 1-ac yl-sn-glycerol-3-phosphate acyltransferase PlsC, is a critical interme diate step in the biosynthesis of membrane glycerophospholipids. A Tn9 16-generated mutant of a serogroup a meningococcal strain was identifi ed that exhibited increased amounts of capsular polysaccharide, as sho wn by colony immunoblots, and a threefold increase in the number of as sembled pill. The single, truncated 3.8 kb Tn916 insertion in the meni ngococcal mutant was localized within a 771 bp open reading frame. The gonococcal equivalent of this gene was identified by transformation w ith the cloned meningococcal mutant gene, In N. gonorrhoeae, the mutat ion increased piliation fivefold. The insertions were found to be with in a gene that was subsequently designated nlaA (neisserial IPA acyltr ansferase). The predicted neisserial LPA acyltransferases were homolog ous (>20% identity, >40% amino acid similarity) to the family of PlsC protein homologues, A cloned copy of the meningococcal nlaA gene compl emented in trans a temperature-sensitive E. coil PlsC(ts-) mutant. Tn9 16 and Omega-cassette insertional inactivations of the neisserial nlaA genes altered the membrane glycerophospholipid compositions of both N . meningitidis and N. gonorrhoeae but were not lethal, Therefore, the pathogenic Neisseria spp. appear to be able to utilize alternative enz yme(s) to produce phosphatidic acid, This hypothesis is supported by t he observation that, although the amounts of mature glycerophospholipi ds were altered in the meningococcal and the gonococcal nlaA mutants, glycerophospholipid synthesis was detectable at significant levels. In addition, acyltransferase enzymatic activity, while reduced in the go nococcal nlaA mutant, was increased in the meningococcal nlaA mutant. We postulate that the pathogenic Neisseria spp, are able to utilize al ternate acyltransferases to produce glycerophospholipids in the absenc e of nlaA enzymatic activity. Implementation of these secondary enzyme s results in alterations of glycerophospholipid composition that lead to pleiotropic effects on the cell surface components, including effec ts on capsule and piliation.