Download IS91 transposase is related to the rolling-circle

Nucleic Acids Research, Vol. 20, No. 13 3521
© 1992 Oxford University Press
IS91 transposase is related to the rolling-circle-type
replication proteins of the pUB110 family of plasmids
M.Victoria Mendiola and Fernando de la Cruz*
Departamento de Biologfa Molecular, Universidad de Cantabria, C. Herrera Oria s/n, 39011
Santander, Spain
Submitted April 22, 1992
EMBL accession no. X17114
IS91 is an insertion sequence of 1830 bp, which was isolated
from a hemolysin plasmid of Escherichia coli. It has inverted
repeats of only 8 bp and, unusually, shows an absolute target
site specificity [GAAC/CAAG] (1,2). IS97 is related to IS807
from Pseudomonas syringae (3). In particular, their transposases
are 35% identical proteins of 426 and 410 amino acids
respectively (2,3). Apart from this, IS91 is unrelated to other
presently known IS elements.
Figure 1 shows the four conserved motifs between the
IS91/IS8O1 transposases and a family of five replication proteins
of plasmids pUBHO, pLABlOOO, pLPl, pFTB14 and pC194
from gram-positive bacteria (4, 5). Motif I shows a cysteine-rich
sequence which is a potential metal-binding domain. Motif II
includes an H.H.H motif. This motif is also present in a family
of nickases/relaxases involved in oriT nicking for conjugal DNA
transfer in a variety of plasmids, and in the VirD2 proteins
responsible for nicking of the T-DNA of the Ti plasmid of
Agrobacterium tumefaciens (7). Motif IH contains the Y ... Y..K
sequence. This motif is also found in the gpA protein of the
ssDNA phage 0X-174 (Figure 1) and related phages, and contains
the two tyrosines forming the catalytic site of these topoisomerases
(8). Motif IV contains the invariant sequence R ... Y.G; the Rep
protein of pC194 finishes before this motif.
The pUBl 10 and related Rep proteins produce a single-strand
nick in a specific site of the plasmid (the leading strand origin
of replication), and this nick results in single-strand replication
by the rolling circle mechanism (4, 6). Their similarity to the
transposases of IS91/IS801 suggests that transposition of these
elements also involves single-strand nicking by the transposases,
followed by single-stranded rolling-circle replication of the
transposon. This will be in contrast to any of the mechanisms
of transposition that have been shown or suggested for other
elements (9). Finally, it can be speculated that the IS97
transposase appeared by evolution of a plasmid Rep protein,
suggesting a mechanism to explain the origin of transposable
elements.
ACKNOWLEDGEMENTS
We thank John Grinsted for critical reading and correction of
the manuscript. The work was financially supported by the
C.I.C.Y.T., Spain (project number BIO90-0661).
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
9.
Mendiola el at. (1989) Mol. Microbiot. 3, 979-984.
Mendiola et at. (1992)7. Baderiot. 174, 1345-1351.
Romantschuk et at. (1991) Mol. Microbiol. 5, 617-622.
Bouia etal. (1989) Plasmid 22, 185-192.
Josson el at. (1990) J. Bacterial. 172, 3089-3099.
Noviclc (1989) Annu. Rev. Microbiol. 43, 537-565.
Pansegrau and Lanka (1991) Nucleic Acids Res. 19, 3455.
van Mansfeld et at. (1986) Nucleic Acids Res. 14, 4229-4238.
Berg and Howe (1989) Mobile DNA. American Society for Microbiology,
Washington DC.
10. Sanger et at. (1978) J. Mol. Biol. 125, 225-246.
J 3
gpA (0X-174)
*° GRLHFHAVHFH JW
* YVAKYVNKKSD 3 W
TnpA (1891)
"CKSRSCPHCGVK 1M
HHPHIHLSTTA
YFGSYLKKPPV
RKVRYYGFL
TnpA (IS801)
"CHCRACPSCGKK w WHPHVHLSVTA "'YLGRYLKKPPI 3a RMIRYFGFL
Rep
Rep
Rep
Rep
Rep
(pUBHO)
(pIABlOOO)
(pLPl)
(pFTB14)
(pC194)
CONSENSUS
"CKSRLCPMCNWR 1i0
YNQHMHVLVCV I2I
^ETAKYPVKDTD 2znM RLISYGGLL
"CKSRLCPLCNWR ww 00 YHQHMHVLLFV 223
ETAKYPVKDTD
RQISYGGLF
"CHKRLCPLCNWR
YNQHLHVLLFV ETAKYEVKSAD °* RQISYGGLL
*2CKVRLCP»ICAWR 1U
"* YHPHFHVLLPV "'EISKYPVKDTD aa RLIGYGGIL
"CKNRFCPVCAMR
YNPHFHVLIAV ""EMAKYSGKDSD
C+.R.CP.C..+
*—H*H*..
.Y..K..
R.*.Y.G**
Figure 1. Motif alignment of the \S91/iS80I transposases (2, 3) with five DNA Rep proteins of a family of plasmids of gram-positive bacteria (4, 5), and with
the gpA protein of bacteriophage i^X-174 (10). Numbers indicate the sequence positions of the first amino acid residues shown. The CONSENSUS points out the
invariant amino acids, or groups of related amino acids (+ basic; • « hydrophobic).
• To whom correspondence should be addressed