Alignment of the RC motifs in the Helitrons. Following
is a list of the RCR initiator-like proteins: SVTS2 (GenBank accession
no. AAF18310, the SVTS2 ssDNA spiroplasma plectrovirus); Rep_SC
(BAA34784, the pSA1.1 conjugative plasmid from Streptomyces
cyaneus); Rep_BB (BAA07788, the pHT926 Bacillus
borstelensis cryptic plasmid); Rep_AA (AAC37125, the
pVT736–1 RCR plasmid from Actinobacillus
actinomycetemcomitans); and Pf3 (AAA88392, the Pf3 ssDNA
bacteriophage from Pseudomonas aeruginosa). Color
shading shows different physicochemical properties of conserved amino
acids (17). Conserved tyrosines, corresponding to the RCR
nicking/ligation catalytic center, are marked by dots.