Characterization of a Legionella pneumophila gene encoding a lipoprotein antigen

A prominent 19kDa surface antigen of Legionella pneumophila , cloned in Escherichia coli , was found to be intimately associated with peptidoglycan. The DNA region encoding this antigen was mapped on an 11.9kb plasmid by means of deletion analysis and transposon mutagenesis. PhoA + gene fusions, generated by Tn phoA insertions into this region, confirmed the presence of a gene encoding a secreted protein. PhoA + transposon insertions were also associated with loss of the 19 kDa antigen in immunoassay s using a monoclonal antibody (mAb1E9) and the replacement of the 19kDa antigen with larger fusion proteins in immunoblots using Legionella immune serum. A 1540bp PstI fragment carrying the gene was sequenced, and the open reading frame encoding the antigen was identified. The gene encodes a polypeptide 176 amino acid residues long and 18913Da in size. The presence of a signal sequence of 22 amino acids with a consensus sequence for cleavage by signal peptidase II indicates that the antigen is a lipoprotein, and striking similarity with peptidoglycan-associated lipoproteins (PALs) from E. coli (51% amino acid homology) and Haemophilus influenzae (55% homology) is noted. We conclude that the 19kDa antigen of L. pneumophila is the structural equivalent of the PAL found in other Gram-negative species and suggest that its post-translational acylation may explain its potency as an immunogen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75712/1/j.1365-2958.1991.tb00824.x.pd

Molecular analysis of the Corynebacterium glutamicum lysl gene involved in lysine uptake

Seep-Feldhaus AH, Kalinowski J, Pühler A. Molecular analysis of the Corynebacterium glutamicum lysl gene involved in lysine uptake. MOLECULAR MICROBIOLOGY. 1991;5(12):2995-3005.Two Corynebacterium glutamicum mutants defective in lysine uptake were identified by analysing mutants resistant to S-(2-aminoethyl)-cysteine (AEC). A 5.6 kb genomic DNA fragment restoring AEC sensitivity and lysine uptake was isolated. A 4.2 kb subfragment was sequenced and three open reading frames were identified. Subcloning and gene disruption experiments showed that only the first open reading frame, termed lysI, is involved in lysine uptake. LysI consists of 501 amino acids with a M(r) of 53600. The hydrophobicity profile suggests that the lysI gene product is an integral membrane protein with 13 transmembrane segments. The amino acid sequence of lysI displays strong homology to that of the arcD gene product of Pseudomonas aeruginosa, which is proposed to act as an arginine-ornithine antiporter. Investigation of the influence of the lysI gene on lysine secretion suggests the existence of a separate lysine efflux system in C. glutamicum