SARS coronavirus encodes non-structural protein 13 (nsP13), a nucleic acid helicase/NTPase belonging to superfamily 1 helicase, which efficiently unwinds both partial-duplex RNA and DNA. In this study, unwinding of DNA substrates that had different duplex lengths and 5′-overhangs was examined under single-turnover reaction conditions in the presence of excess enzyme. The amount of DNA unwound decreased significantly as the length of the duplex increased, indicating a poor in vitro processivity. However, the quantity of duplex DNA unwound increased as the length of the single-stranded 5′-tail increased for the 50-bp duplex. This enhanced processivity was also observed for duplex DNA that had a longer single-stranded gap in between. These results demonstrate that nsP13 requires the presence of a long 5′-overhang to unwind longer DNA duplexes. In addition, enhanced DNA unwinding was observed for gapped DNA substrates that had a 5′-overhang, indicating that the translocated nsP13 molecules pile up and the preceding helicase facilitate DNA unwinding. Together with the propensity of oligomer formation of nsP13 molecules, we propose that the cooperative translocation by the functionally interacting oligomers of the helicase molecules loaded onto the 5′-overhang account for the observed enhanced processivity of DNA unwinding.
Although foreign body ingestion is relatively common in children aged 6 months-3 years, small bowel obstruction rarely develops, and few cases require surgical interventions. We report a case of 12-month-old girl who presented to the emergency department with new-onset seizure after projectile bilious vomiting. The initial diagnosis was seizure caused by hyponatremia based on laboratory findings, plain abdominal radiograph, brain magnetic resonance imaging, and electroencephalography. Despite fluid resuscitation, clinical manifestations did not improve, and severe ileal obstruction was found on computed tomography. Emergency laparoscopy showed a foreign body (a water bead [superabsorbent polymer], 3 cm in diameter) that was subsequently removed by enterotomy. After the surgery, bilious vomiting continued, and gastrografin did not pass on fluoroscopy. The second laparoscopy showed a residual foreign body that was crushed and then removed by minimal enterotomy. She was discharged in good condition 5 days after the second surgery. This case suggests a particular danger of water beads as foreign bodies and the need for differential diagnosis of multiple foreign bodies in children with poor communication skills.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.