DraIII is a type IIP restriction endonucleases (REases) that recognizes and creates a double strand break within the gapped palindromic sequence CAC↑NNN↓GTG of double-stranded DNA (↑ indicates nicking on the bottom strand; ↓ indicates nicking on the top strand). However, wild type DraIII shows significant star activity. In this study, it was found that the prominent star site is CAT↑GTT↓GTG, consisting of a star 5' half (CAT) and a canonical 3' half (GTG). DraIII nicks the 3' canonical half site at a faster rate than the 5' star half site, in contrast to the similar rate with the canonical full site. The crystal structure of the DraIII protein was solved. It indicated, as supported by mutagenesis, that DraIII possesses a ββα-metal HNH active site. The structure revealed extensive intra-molecular interactions between the N-terminal domain and the C-terminal domain containing the HNH active site. Disruptions of these interactions through site-directed mutagenesis drastically increased cleavage fidelity. The understanding of fidelity mechanisms will enable generation of high fidelity REases.
Amino Acid Sequence ; Base Sequence ; Calorimetry, Differential Scanning ; Catalytic Domain ; Crystallography, X-Ray ; DNA ; metabolism ; DNA Cleavage ; Deoxyribonucleases, Type II Site-Specific ; chemistry ; genetics ; metabolism ; Escherichia coli ; metabolism ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Recombinant Proteins ; chemistry ; genetics ; metabolism ; Sequence Alignment ; Substrate Specificity

Objective To analyze the risk factors of nosocomial infection among the patients in neuro-surgical ICU,and to construct the risk prediction model to provide reference for the prediction of nosocomial infection in neurosurgical ICU patients.Methods The clinical data of 280 patients admitted and treated in the neurosurgery ICU of this hospital from January 2021 to December 2022 were retrospectively analyzed.The pa-tients were divided into the infection group and non-infection group based on whether or not nosocomial infec-tion occurring,140 cases in each group.A total of 196 patients were extracted as the training set by a ratio of 7︰3 for constructing the model,while the remaining 84 patients served as the validation set for conducting the internal verification.The logistic regression was used to analyze the risk factors of nosocomial infection in the neurosurgery ICU patients,and a predictive model was established.The receiver operating characteristic (ROC) curve was drawn to evaluate the predictive effect of the model.Results The multivariate logistic re-gression analysis indicated that old age,long surgery time,catheter use and glucocorticoids use were screened as the main risk factors of nosocomial infection occurrence in neurosurgery ICU patients.The nomogram mod-el was constructed based on the results of multivariate analysis,the area under the curve of training set and validation set were 0.796 and 0.875,respectively.The correcting model reflected good consistency between actual diagnosis and predictive diagnosis.Conclusion The model constructed in this study has the high predic-tive value for the nosocomial infection occurrence risk in the patients of the neurosurgery ICU.