Disease relevance of sapA

• Inactivation of the sapA to sapF locus of Erwinia chrysanthemi reveals common features in plant and animal bacterial pathogenesis [1].
• It has five open reading frames that are closely related (71% overall amino acid identity) and are in the same order as those of the sapA to sapF operon from Salmonella typhimurium [1].
• Rearrangement of sapA homologs with conserved and variable regions in Campylobacter fetus [2].
• All eight sapA homologues were expressed in Escherichia coli as antigenic proteins and reattached to the surface of SLP- strain 23B, indicating their conserved function [3].

High impact information on sapA

• Analysis of sapA and sapA1 and partial analysis of sapA2 indicate that a block of approximately 600 bp beginning upstream and continuing into the open reading frames is completely conserved, and then the sequences diverge completely, but immediately downstream of each gene is another conserved 50-bp sequence [2].
• We propose that site-specific reciprocal recombination between sapA homologs leads to expression of divergent S-layer proteins as one of the mechanisms that C. fetus uses for antigenic variation [2].
• The Campylobacter fetus surface layer proteins (SLPs), encoded by five to nine sapA homologues, are major virulence factors [3].
• Promoter-specific polymerase chain reactions (PCRs) and sapA homologue-specific reverse transcription (RT)-PCRs showed that the unique sapA promoter can potentially express all eight sapA homologues [3].
• Southern hybridizations of the revertants showed rearrangement of sapA homologues and retention of the km marker [4].

Biological context of sapA

• These results indicate that the interaction of antimicrobial peptides from the host with the sapA to sapF operon from the pathogen plays a similar role in animal and in plant bacterial pathogenesis [1].
• High-frequency S-layer protein variation in Campylobacter fetus revealed by sapA mutagenesis [4].
• A 35-bp sequence, present upstream of the putative sapA promoter, and a similar sequence (30 of 35 nucleotides identical) upstream of sapK were shown to be necessary for proper expression and could thus be possible targets for transcriptional activation [5].
• Cloning and sequencing of the entire 6.2-kb invertible region from C. fetus 23D revealed a probable 5.6-kb operon of four overlapping genes (sapCDEF, with sizes of 1,035, 1,752, 1,284, and 1,302 bp, respectively) transcribed in the opposite direction from sapA [6].
• Pulsed-field gel electrophoresis and then Southern blotting with the conserved N-terminal region of the sapA homologs as a probe showed that these genes were tightly clustered on the chromosome [7].

References