The surface array protein (SAP) of Campylobacter fetus strain TK is encoded by seven homologous sapA genes clustered on the chromosomal DNA. The spontaneously arising variant strain TK(SAP-) produces no SAP and carries an approximately 10-kb chromosomal deletion. To elucidate the mechanism underlying the loss of SAP synthesis, we analyzed the region containing the sapA homologues and the deletion. We constructed a physical map of the sapA cluster region by aligning the clones that contain sapA homologues. These analyses demonstrated that all sapA homologues were located within a limited region of about 50 kb of chromosomal DNA of strain TK. The TK(SAP-) deletion was located within this cluster and was 13.3 kb in size. The deletion occurred between two sapA homologues and resulted in the formation of a chimeric sapA homologue in the variant strain. Sequence analysis of the upstream regions and the conserved regions of all sapA homologues revealed a high degree of similarity. However, only one sapA homologue contained a putative promoter sequence. This promoter sequence was located in the deleted region. Thus, the deletion of the promoter appears to be responsible for the loss of SAP expression in TK(SAP-).
All Science Journal Classification (ASJC) codes
- Molecular Biology