The following text describes a protein:
Function:
Modifies the topological state of DNA by introducing positive supercoils in an ATP-dependent process; dATP also allows positive supercoiling. Increases the linking number in steps of +1. Only this subunit binds ATP, it does so in a DNA- and RgyA-independent manner. Hydrolyzes ATP only in the presence of DNA. The RgyA subunit transiently cleaves a single DNA strand and remains covalently bound to the 5' DNA end probably through a tyrosine residue. It changes linking number in steps of one, and nicks DNA preferentially at 5'-CNNN | 3'-sites with a strong preference for 4 pyrimidine residues. There are about 1000 heterodimers per cell. May be involved in rewinding the DNA strands in the regions of the chromosome that have opened up to allow transcription or replication (By similarity); This subunit expressed in E.coli only has DNA-dependent ATPase activity at 80 degrees Celsius. Reverse gyrase activity is reconstituted after incubation at 80 degrees Celsius for 5 minutes, positive supercoiling requires ATP and Mg(2+). In the presence of ATP it binds and nicks substrate but does not make closed product.
Miscellaneous:
MISCELLANEOUS: This enzyme is the only unique feature of hyperthermophilic bacteria/archaea known and seems to be essential for adaptation to life at high temperatures. It may play a role in stabilization of DNA at high temperatures.
Subcellular Localization:
Cytoplasm.
Domain:
Introduction of positive supercoils requires the cooperation of both the helicase-like and topoisomerase domains of the 2 subunits. The helicase-like domain probably does not directly unwind DNA, but more likely acts by driving ATP-dependent conformational changes within the whole enzyme. A beta hairpin in the 'latch' region of the N-terminal domain plays a regulatory role in the enzyme, repressing topoisomerase activity in the absence of ATP and preventing the enzyme from acting as an ATP-independent relaxing enzyme; it also helps to coordinate nucleotide hydrolysis by the ATPase domain with the supercoiling activity of the topoisomerase domain.
Sequence:
MVLKRAADMVPKGFRDLVEPILDDCADLEELADRVVETEMEPDEVRRRDVGNTDSNEPVAIFGSSCVLCGGDCSSVRLTSRIGICERCLPVDTETLREVLKEARKRHGYVGEALLMFILVERYSPDRVEEFFRRYVWPELFTEIVDRVFDRATGFRLYSAQRVWTRRLVKGCSFSILAPTGTGKTSWGSLVAAVFGHAGRRVYYLVPTTTLVRQVENRIKGFARDAELDVDVVAYHAAMPTQAKREALERISSGDFDVLITTAQFLVHRVEDLEKLNFDLILVDDVDAIIRGTGRNVDRVLRVAGLEQEEIDSAYRLATLRRRYYSLRDWLRSLEDRGDKRAERVREELREVEREIEELEELLKRVKKERDLARIVFMSATGAAAPSRRLAVVRELFDFEVGAGGEGLRNIQDIAVISEPSPEAVERIVRKAGVKGGLIFVPQRLPGEKKAREIVEELAEHLRSSGIEARAIHAGTPAEEREEAIDGFSEGDVDVLVAVASPYGVIVRGLDLPQAARYAVFYGVPRQRIRLTPREEDLKDPTYVASALSNLARLLDDRRARSRLEGVAGRLWRIIRRGTWIRERLEEAVEPLSLNTLMKLAKRDPEDIAEQLDVDRWLARHVQTLAEGVRELTRLLGDPDRVKALAEEATTVAVYEEGEEAYLEVPDLRTYIQASGRVSRLFAGGVTFGLSFVLCPEDERELRTLNGLIRRMSYTYGSEFEWRSYPKSLDMKEIGLELKEISDEELEELVRKVDEDRERVRKVLAGELKPEETGRLARSALMIVESPNKARMIASLFSQRPSRRRLNGGVAYEAAADGLHLTVVATQGHVADLVEEPGVHGVLRIDERWVPMYDVLGRCSECGEQVVGSEECPNCGGEVELKTPLLESIRELASEADVILIGTDPDTEGEKIGWDVFNYLGWTTAQVYRTEFHEVTRRGISEALKEESWKNVDAGRVSAQILRRVADRWIGFSLSQDLWDVFKHLEIKLGELPSGSRIEVRLDIPSGVEVVDFRRTFDEDSSVRSRSVRLRREGDEYVVRTRISRGGDVTYTATLLDPNRKLGDRNGVRPELVRVRASVNGEPVDPNVKLEPMTWLSAGRVQTPVLGWIIDRAREYRETEFYACRAEVPADDVTIRALIEELKVPRALTEKLDEATIRVLSKIAEEGPDAEFSEEEVGRFTETELFERKDGRYRLSEEGRKVLESEGVIGLMLHLAGVSGR