2gai
From Proteopedia
Structure of Full Length Topoisomerase I from Thermotoga maritima in triclinic crystal form
Structural highlights
FunctionTOP1_THEMA Releases the supercoiling and torsional tension of DNA, which is introduced during the DNA replication and transcription, by transiently cleaving and rejoining one strand of the DNA duplex. Introduces a single-strand break via transesterification at a target site in duplex DNA. The scissile phosphodiester is attacked by the catalytic tyrosine of the enzyme, resulting in the formation of a DNA-(5'-phosphotyrosyl)-enzyme intermediate and the expulsion of a 3'-OH DNA strand. The free DNA strand then undergoes passage around the unbroken strand, thus removing DNA supercoils. Finally, in the religation step, the DNA 3'-OH attacks the covalent intermediate to expel the active-site tyrosine and restore the DNA phosphodiester backbone (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedDNA topoisomerases are a family of enzymes altering the topology of DNA by concerted breakage and rejoining of the phosphodiester backbone of DNA. Bacterial and archeal type IA topoisomerases, including topoisomerase I, topoisomerase III, and reverse gyrase, are crucial in regulation of DNA supercoiling and maintenance of genetic stability. The crystal structure of full length topoisomerase I from Thermotoga maritima was determined at 1.7A resolution and represents an intact and fully active bacterial topoisomerase I. It reveals the torus-like structure of the conserved transesterification core domain comprising domains I-IV and a tightly associated C-terminal zinc ribbon domain (domain V) packing against domain IV of the core domain. The previously established zinc-independence of the functional activity of T.maritima topoisomerase I is further supported by its crystal structure as no zinc ion is bound to domain V. However, the structural integrity is preserved by the formation of two disulfide bridges between the four Zn-binding cysteine residues. A functional role of domain V in DNA binding and recognition is suggested and discussed in the light of the structure and previous biochemical findings. In addition, implications for bacterial topoisomerases I are provided. Crystal structure of full length topoisomerase I from Thermotoga maritima.,Hansen G, Harrenga A, Wieland B, Schomburg D, Reinemer P J Mol Biol. 2006 May 19;358(5):1328-40. Epub 2006 Mar 23. PMID:16600296[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
| ||||||||||||||||||
