M. Gibert et al., CLOSTRIDIUM SPIROFORME TOXIN GENES ARE RELATED TO CLOSTRIDIUM-PERFRINGENS LOTA TOXIN GENES BUT HAVE A DIFFERENT GENOMIC LOCALIZATION, Systematic and applied microbiology, 20(3), 1997, pp. 337-347
Clostridium spiroforme toxin belongs to the iota toxin family and cons
ist of an ADP-ribosyltransferase component (Sa) and a binding componen
t (Sb) which is involved in the binding and internalization of the tox
in within the cell. In this study, the respective genes, sas and sbs,
were characterized. The genes are orientated in the same way as the C.
perfringens iota toxin genes and the C. difficile ADP-ribosyltransfer
ase (CDT) genes. The sas gene is located upstream of the sbs gene. The
genes are transcribed in the same orientation, and are separated by a
short (41 bp) non coding sequence. The encoded proteins Sa and Sb are
similar (about 80% identity) to the iota toxin and CDT, and these tox
ins have the same domain organization. In contrast to the iota toxin g
enes which are present on large plasmids in C. perfringens E, C, spiro
forme toxin and CDT genes are present on the chromosome in the C. spir
oforme and C. difficile strains analyzed, although these strains also
contain large plasmids. A variation of the iota toxin sequences (80% i
dentity) was observed in 3 of 4 C. perfringens E strains, and one stra
in had only the enzymatic component gene.