2l8b

Publication Abstract from PubMed

TraI, the F plasmid-encoded nickase, is a 1756 amino acid protein essential for conjugative transfer of plasmid DNA from one bacterium to another. Although crystal structures of N- and C-terminal domains of F TraI have been determined, central domains of the protein are structurally unexplored. The central region (between residues 306 and 1520) is known to both bind single-stranded DNA (ssDNA) and unwind DNA through a highly processive helicase activity. Here, we show that the ssDNA binding site is located between residues 381 and 858, and we also present the high-resolution solution structure of the N-terminus of this region (residues 381-569). This fragment folds into a four-strand parallel beta sheet surrounded by alpha helices, and it resembles the structure of the N-terminus of helicases such as RecD and RecQ despite little sequence similarity. The structure supports the model that F TraI resulted from duplication of a RecD-like domain and subsequent specialization of domains into the more N-terminal ssDNA binding domain and the more C-terminal domain containing helicase motifs. In addition, we provide evidence that the nickase and ssDNA binding domains of TraI are held close together by an 80-residue linker sequence that connects the two domains. These results suggest a possible physical explanation for the apparent negative cooperativity between the nickase and ssDNA binding domain. Proteins 2012; (c) 2012 Wiley Periodicals, Inc.

Solution structure and small angle scattering analysis of TraI (381-569).,Wright NT, Raththagala M, Hemmis CW, Edwards S, Curtis JE, Krueger S, Schildbach JF Proteins. 2012 Aug;80(9):2250-61. doi: 10.1002/prot.24114. Epub 2012 Jun 18. PMID:22611034^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.