FIG. 4.

Characteristics of IS891-related ISs. (/, presumptive left end of target site). (A) Border regions of copies of IS891. (B) Border regions of members of IS891-related clusters 2 (the top five) and 3. Lowercase tag and tga are the termination codons of the right-hand transposase ORF. (C) Result of a BLASTn search against the A. variabilis genome as target with, as query, the presumptive pretransposition region of IS(alr2167, alr2168) (see panel B, cluster 3), shows that tgac (underlined) is adjacent to the site of insertion of IS(alr2167, alr2168). (D) Border regions of members of IS891-related cluster 6, in which one cannot distinguish the L end (//, end of region of commonality) from a target site. (E) tBLASTx illustrates the greater similarity of IS(all7148, alr7149), IS(avaB0100, avaB0101), and a region from Cyanothece sp. strain PCC 7424, relative to IS(all7008, alr7009). In panels E and F, colors of bars correspond to alignment scores: red, ≥200; violet, 80 to 200; green, 50 to 80; blue, 40 to 50; and black, <40. ORFs are depicted as arrows with gray shafts from vertical lines to horizontal arrowheads. (F) The result of using IS(all7008, alr7009) as query supports the interpretation that IS(alr7386′, etc.), inserted at the vertical arrowhead in panels E and F (see also Fig. 5, below), is within IS(all7008, alr7009). (G) The R border of IS(all3371, alr3372) in cluster 6 of the IS200-IS605 family shows an unusual example of an IS891-related IS in which the R end, near the (lowercase) termination codon tga of alr3372, may terminate in a variation of TGTCAA.