PMID:15466871

Citation	Hsieh, TJ, Farh, L, Huang, WM and Chan, NL (2004) Structure of the topoisomerase IV C-terminal domain: a broken beta-propeller implies a role as geometry facilitator in catalysis. J. Biol. Chem. 279:55587-93
Abstract	Bacteria possess two closely related yet functionally distinct essential type IIA topoisomerases (Topos). DNA gyrase supports replication and transcription with its unique supercoiling activity, whereas Topo IV preferentially relaxes (+) supercoils and is a decatenating enzyme required for chromosome segregation. Here we report the crystal structure of the C-terminal domain of Topo IV ParC subunit (ParC-CTD) from Bacillus stearothermophilus and provide a structure-based explanation for how Topo IV and DNA gyrase execute distinct activities. Although the topological connectivity of ParC-CTD is similar to the recently determined CTD structure of DNA gyrase GyrA subunit (GyrA-CTD), ParC-CTD surprisingly folds as a previously unseen broken form of a six-bladed beta-propeller. Propeller breakage is due to the absence of a DNA gyrase-specific GyrA box motif, resulting in the reduction of curvature of the proposed DNA binding region, which explains why ParC-CTD is less efficient than GyrA-CTD in mediating DNA bending, a difference that leads to divergent activities of the two homologous enzymes. Moreover, we found that the topology of the propeller blades observed in ParC-CTD and GyrA-CTD can be achieved from a concerted beta-hairpin invasion-induced fold change event of a canonical six-bladed beta-propeller; hence, we proposed to name this new fold as "hairpin-invaded beta-propeller" to highlight the high degree of similarity and a potential evolutionary linkage between them. The possible role of ParC-CTD as a geometry facilitator during various catalytic events and the evolutionary relationships between prokaryotic type IIA Topos have also been discussed according to these new structural insights.
Links	PubMed Online version:10.1074/jbc.M408934200
Keywords	Amino Acid Motifs; Catalysis; Crystallography, X-Ray; DNA/chemistry; DNA Gyrase/chemistry; DNA Topoisomerase IV/chemistry; Geobacillus stearothermophilus/enzymology; Models, Biological; Models, Molecular; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Selenomethionine/chemistry; Transcription, Genetic
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