Sequence analysis. (A) Sequence
comparison to DnaE proteins. The Ssp DnaE extein
sequences (Ssp) are aligned with corresponding DnaE
sequences of E. coli (Eco),
Bacillus subtilis (Bsu), and
Mycobacterium tuberculosis (Mtu). Only
sequences proximal to the intein sequences (Int-n and Int-c) are shown,
whereas the number of omitted residues at the N- and C-termini are
shown in parentheses. Symbols: − represent gaps introduced to optimize
the alignment; ∗ and . mark positions of identical and similar
amino acids, respectively. (B) Sequence comparison to
inteins. The Ssp DnaE intein sequences
(Ssp DnaE), consisting of Int-n and Int-c as indicated,
are aligned with corresponding sequences of Rhodothermus
marinas DnaB intein (Rma DnaB),
Synechocystis sp. PCC6803 DnaB intein
(Ssp DnaB), and Porphyra purpurea
chloroplast DnaB intein (Ppu DnaB). In the
Rma DnaB intein and the Ssp DnaB intein,
only sequences relating to Int-n and Int-c are shown, whereas the
number of omitted residues are shown in parentheses. Putative intein
motifs (Blocks A, B, F, and G) are underlined, with several critical
residues marked by ∗.