Novel protein fold discovered in the PabI family of restriction enzymesMiyazono, K., Watanabe, M., Kosinski, J., Ishikawa, K., Kamo, M., Sawasaki, T., Nagata, K., Bujnicki, J.M., Endo, Y., Tanokura, M., Kobayashi, I.
(2007) Nucleic Acids Res. 35: 1908-1918
- PubMed: 17332011
- DOI: 10.1093/nar/gkm091
- PubMed Abstract:
Although structures of many DNA-binding proteins have been solved, they fall into a limited number of folds. Here, we describe an approach that led to the finding of a novel DNA-binding fold. Based on the behavior of Type II restriction-modification ...
Although structures of many DNA-binding proteins have been solved, they fall into a limited number of folds. Here, we describe an approach that led to the finding of a novel DNA-binding fold. Based on the behavior of Type II restriction-modification gene complexes as mobile elements, our earlier work identified a restriction enzyme, R.PabI, and its cognate modification enzyme in Pyrococcus abyssi through comparison of closely related genomes. While the modification methyltransferase was easily recognized, R.PabI was predicted to have a novel 3D structure. We expressed cytotoxic R.PabI in a wheat-germ-based cell-free translation system and determined its crystal structure. R.PabI turned out to adopt a novel protein fold. Homodimeric R.PabI has a curved anti-parallel beta-sheet that forms a 'half pipe'. Mutational and in silico DNA-binding analyses have assigned it as the double-strand DNA-binding site. Unlike most restriction enzymes analyzed, R.PabI is able to cleave DNA in the absence of Mg(2+). These results demonstrate the value of genome comparison and the wheat-germ-based system in finding a novel DNA-binding motif in mobile DNases and, in general, a novel protein fold in horizontally transferred genes.
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.