Abstracts (poster) - Wissenschaft Online

Tomasz Jurkowski, Nils Anspach, Lilia Kulishova, Wolfgang Nellen, Albert Jeltsch
The M.EcoRV DNA methyltransferase uses DNA bending for
recognition of an expanded EcoDam recognition site.
The M.EcoRV DNA methyltransferases recognizes GATATC sites. It is related to EcoDam,
which methylates GATC sites. The DNA binding domain of M.EcoRV is similar to that of
EcoDam suggesting a similar mechanism of DNA recognition. We show that K11 of
M.EcoRV is involved in recognition of Gua1 and R128 contacts the Gua in base pair six.
These residues correspond to K9 and R124 in EcoDam, which recognize the Gua residues
in both strands of the Dam recognition sequence, indicating that M.EcoRV and EcoDam
make similar contacts to outermost base pair of their recognition sequences. In contrast
to EcoDam M.EcoRV considerably bends the DNA (59±4°) suggesting indirect readout of
the AT rich inner sequence. DNA bending could be a general mechanism for recognition
of expanded target sites during evolution. R128A is inefficient in DNA bending and
binding whereas K11A shows relaxed sequence specificity. These results suggest that
the Gua6-R128 contact forms early and leads to a pause in the linear diffusion of the
enzyme along the DNA. After DNA bending, the K11- Gua1 contact forms.
Literature
Horton, J.R., Liebert, K., Hattman, S., Jeltsch, A. & Cheng, X. (2005) Transition from
nonspecific to specific DNA interactions along the substrate-recognition pathway of dam
methyltransferase. Cell, 121, 349-361.
Beck, C., Cranz, S., Solmaz, M., Roth, M. & Jeltsch, A. (2001) How does a DNA
interacting enzyme change its specificity during molecular evolution? A sitedirected
mutagenesis study at the DNA binding site of the DNA-(Adenine-N6)-methyltransferase
EcoRV. Biochemistry, 40, 10956-10965.
contact:
Tomasz Jurkowski
Jacobs University Bremen
Biochemistry
t.jurkowski@jacobs-university.de
Campus Ring 1
28759 Bremen (Germany)