I. Saves et al., Identification of the first eubacterial endonuclease coded by an intein allele in the pps1 gene of mycobacteria, NUCL ACID R, 29(21), 2001, pp. 4310-4318
A survey of a vast range of mycobacterial strains led us to discover a new
Pps1 intein allele in Mycobacterium gastri which differs from those of Myco
bacterium tuberculosis and Mycobacterium leprae in both its sequence and in
sertion site. While little is known about Pps1, except that it belongs to t
he YC24 family of ABC transporters, we show that, unlike the other inteins
described so far from Eubacteria, the MgaPps1 intein possesses a specific e
ndonuclease activity. The intein is the first eubacterial intein to be char
acterised as an endonuclease. Like other intein endonucleases, its minimal
sequence for recognition and cleavage is quite large, with 22 bp spanning t
he Pps1-c site. The fact that an active endonuclease is found among the myc
obacterial inteins supports the concept of a cyclical model of invasion by
horizontal transfer of these genes, followed by degeneration and loss until
a new invasion event, thus explaining their long-term persistence in close
ly related eubacterial species.