Dubaele Sandy, Lourdel Claude, Chène Patrick
Novartis Institutes for Biomedical Research, Oncology Department, CH-4002 Basel, Switzerland.
Biochem Biophys Res Commun. 2006 Mar 17;341(3):828-36. doi: 10.1016/j.bbrc.2006.01.040. Epub 2006 Jan 23.
Helicases contain conserved motifs involved in ATP/magnesium/nucleic acid binding and in the mechanisms coupling nucleotide hydrolysis to duplex unwinding. None of these motifs are located at the adenine-binding pocket of the protein. We show here that the superfamily I helicase, helicase IV from Escherichia coli, utilizes a conserved glutamine and conserved aromatic residue to interact with ATP. Other superfamily I helicases such as, UvrD/Rep/PcrA also possess these residues but in addition they interact with adenine via a conserved arginine, which is replaced by a serine in helicase IV. Mutation of this serine residue in helicase IV into histidine or methionine leads to proteins with unaffected ATPase and DNA-binding activities but with low helicase activity. This suggests that residues located at the adenine-binding pocket, in addition to be involved in ATP-binding, are important for efficient coupling between ATP hydrolysis and DNA unwinding.
解旋酶包含参与ATP/镁/核酸结合以及将核苷酸水解与双链解旋相偶联机制的保守基序。这些基序均不在蛋白质的腺嘌呤结合口袋处。我们在此表明，超家族I解旋酶，即来自大肠杆菌的解旋酶IV，利用一个保守的谷氨酰胺和保守的芳香族残基与ATP相互作用。其他超家族I解旋酶，如UvrD/Rep/PcrA也具有这些残基，但除此之外，它们还通过一个保守的精氨酸与腺嘌呤相互作用，而在解旋酶IV中该精氨酸被丝氨酸取代。将解旋酶IV中的这个丝氨酸残基突变为组氨酸或甲硫氨酸会导致蛋白质的ATP酶和DNA结合活性不受影响，但解旋酶活性较低。这表明位于腺嘌呤结合口袋处的残基，除了参与ATP结合外，对于ATP水解和DNA解旋之间的有效偶联也很重要。
