SEQUENCE-ANALYSIS OF THE SBSA GENE ENCODING THE 130-KDA SURFACE-LAYERPROTEIN OF BACILLUS-STEAROTHERMOPHILUS STRAIN PV72

Bacillus stearothermophilus (Bs) contains a surface-layer (S-layer) pr otein (SbsA), which forms a hexagonal array on the cell wall. In order to understand the structural/functional relationship of SbsA from Bs PV72, the entire nucleotide (nt) sequence of the sbsA gene was determi ned from three overlapping fragments. The 3'-end was cloned and expres sed in Escherichia coli, whereas the 5'-region was amplified from the genome of Bs PV72 by the polymerase chain reaction using two overlappi ng fragments. The open reading frame (3684 nt) of sbsA is predicted to encode a protein of 1228 amino acids (aa). The SbsA is synthesized wi th a leader sequence of 30 aa. The predicted SbsA aa profile was simil ar to most other sequenced S-layer proteins, containing more acidic th an basic aa (pI 5.1) and a very low amount of sulfur-containing aa. Ba sed on aa sequence data, SbsA has weak homology of with the S-layer pr oteins from B. sphaericus, Rickettsia rickettsii, B. brevis HPD31 and B. brevis 47 (OWP).