Disease relevance of lspA

• Although there is no apparent physiological connection, transcriptional analysis demonstrated that, as in some other Gram-negative bacteria, lspA is cotranscribed with ileS in L. pneumophila [1].
• The lsp gene of Escherichia coli encodes the inner membrane enzyme, signal peptidase II (SPase II) [2].
• The signal peptidase II (Isp) gene of Bacillus subtilis [3].
• The lspA Gene, Encoding the Type II Signal Peptidase of Rickettsia typhi: Transcriptional and Functional Analysis [4].
• Cloning and nucleotide sequence of the Enterobacter aerogenes signal peptidase II (lsp) gene [5].

High impact information on lspA

• Here we experimentally verify this prediction by metabolic labeling of subunit b with [14C]palmitic acid and by in vivo interfering with the processing of the prolipoprotein form of subunit b by the antibiotic globomycin, a specific inhibitor of the signal peptidase II [6].
• Unexpectedly, induced expression of MBP27-P was found to have an adverse effect on the processing kinetics of five different nonlipoprotein precursors analyzed, but not precursor Lpp (the major outer membrane lipoprotein) processed by a different enzyme, signal peptidase II [7].
• Taken together, these results strongly support the predicted model for SPase II topology, i.e. this enzyme spans the cytoplasmic membrane four times with both the amino and the carboxyl termini facing the cytoplasm [2].
• A series of lsp-phoA and lsp-lacZ gene fusions have been constructed in vitro to determine the topology of SPase II [2].
• This new cleavage between alanine and lysine residues was resistant to globomycin, a specific inhibitor for signal peptidase II [8].

Chemical compound and disease context of lspA

• Overexpression of R. typhi lspA in Escherichia coli confers increased globomycin resistance, indicating its function as SPase II [4].
• Both non-mutant and mutant signal peptides appeared to be removed at the same unique site between cysteine 21 and serine 22, one residue from the E. coli signal peptidase II processing site [9].
• Globomycin, an inhibitor of lipoprotein-specific signal peptidase II, was lethal for E. coli only when Lpp possessed the C-terminal lysine [10].
• In partition chromatography the recMPT83 partitioned in the water phase while 26 kDa MPB83 in BCG culture filtrate partitioned in the lipid phase confirming that lipidation at the N-terminal cysteine residue occurs after the splitting of the polypeptide chain by signal peptidase II [11].

Biological context of lspA

• The higher transcriptional level of all three genes at the preinfection time point indicates that only live and metabolically active rickettsiae are capable of infection and inducing host cell phagocytosis. lspA and lgt, which are involved in lipoprotein processing, show similar levels of expression [4].
• The lsp gene encoding prolipoprotein signal peptidase (signal peptidase II) is organized into an operon consisting of ileS and three open reading frames, designated genes x, orf149, and orf316 in both Escherichia coli and Enterobacter aerogenes [12].
• Sequence analysis of the pG gene revealed an open reading frame encoding a putative lipoprotein of 196 amino acids with a calculated molecular mass of 22 kDa and a consensus cleavage sequence (Leu-X-Y-Z-Cys) recognized by signal peptidase II [13].
• DNA and amino acid sequence analyses indicated an open reading frame encoding 403 amino acids, with the first 25 amino acids corresponding to a leader peptide terminated by a signal peptidase II processing site of Val-Val-Gly-Cys [14].
• Unmodified prolipoprotein with the putative consensus sequence undergoes sequential modification and processing reactions catalyzed by glyceryl transferase, O-acyl transferase(s), prolipoprotein signal peptidase (signal peptidase II), and N-acyl transferase to form mature lipoprotein [15].

Other interactions of lspA

• The transcription of lspA, lgt (encoding prolipoprotein transferase), and lepB (encoding type I signal peptidase), monitored by real-time quantitative reverse transcription-PCR, reveals a differential expression pattern during various stages of rickettsial intracellular growth [4].
• Radioactive labeling experiments in the presence or absence of globomycin showed that the hybrid protein is modified with a diglyceride and fatty acids and is processed by signal peptidase II, as is the murein lipoprotein [16].

References